Add CONTRIBUTING.md with instructions for contributions

* Add CONTRIBUTING.md with basic instructions for contributions

Signed-off-by: Yaxing Chen <[email protected]>

* Update CONTRIBUTING.md with instructions

Signed-off-by: Yaxing Chen <[email protected]>

* Addressing PR comments:
- Fixed license from BSD to Apache 2.0
- Added DCO information
- Removed unnecessary detailed git instructions
- Reused Hummingbird contributing instructions for bug/issue and PR
- Added formatting
- Added code of conduct

Signed-off-by: Yaxing Chen <[email protected]>

* Fixing typo

Co-authored-by: Adam Fowler <[email protected]>
Signed-off-by: Yaxing Chen <[email protected]>

* Fixing wrong project name in the description

Co-authored-by: Adam Fowler <[email protected]>
Signed-off-by: Yaxing Chen <[email protected]>

---------

Signed-off-by: Yaxing Chen <[email protected]>
Co-authored-by: Adam Fowler <[email protected]>

Author: yaxing

CODE_OF_CONDUCT.md

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+# Code of Conduct
+
+All developers should feel welcome and encouraged to contribute to valkey-swift. Because of this we have adopted the code of conduct defined by [contributor-covenant.org](https://www.contributor-covenant.org). This document is used across many open source 
+communities, and we think it articulates our values well. The full text is copied below:
+
+## Contributor Code of Conduct v1.3
+
+As contributors and maintainers of this project, and in the interest of
+fostering an open and welcoming community, we pledge to respect all people who
+contribute through reporting issues, posting feature requests, updating
+documentation, submitting pull requests or patches, and other activities.
+
+We are committed to making participation in this project a harassment-free
+experience for everyone, regardless of level of experience, gender, gender
+identity and expression, sexual orientation, disability, personal appearance,
+body size, race, ethnicity, age, religion, or nationality.
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery
+* Personal attacks
+* Trolling or insulting/derogatory comments
+* Public or private harassment
+* Publishing other's private information, such as physical or electronic
+  addresses, without explicit permission
+* Other unethical or unprofessional conduct
+
+Project maintainers have the right and responsibility to remove, edit, or
+reject comments, commits, code, wiki edits, issues, and other contributions
+that are not aligned to this Code of Conduct, or to ban temporarily or
+permanently any contributor for other behaviors that they deem inappropriate,
+threatening, offensive, or harmful.
+
+By adopting this Code of Conduct, project maintainers commit themselves to
+fairly and consistently applying these principles to every aspect of managing
+this project. Project maintainers who do not follow or enforce the Code of
+Conduct may be permanently removed from the project team.
+
+This Code of Conduct applies both within project spaces and in public spaces
+when an individual is representing the project or its community.
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by contacting a project maintainer at [INSERT EMAIL ADDRESS]. All
+complaints will be reviewed and investigated and will result in a response that
+is deemed necessary and appropriate to the circumstances. Maintainers are
+obligated to maintain confidentiality with regard to the reporter of an
+incident.
+
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage],
+version 1.3.0, available at https://www.contributor-covenant.org/version/1/3/0/code-of-conduct.html
+
+[homepage]: https://www.contributor-covenant.org
+

CONTRIBUTING.md

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+# Contributing to Valkey Swift
+
+Thanks for your interest in contributing to Valkey Swift — the Swift client library for Valkey!
+We appreciate all contributions — whether it’s fixing bugs, improving documentation, or adding features.
+
+## Legal
+By submitting a pull request, you represent that you have the right to license your contribution to the community, and agree by submitting the patch
+that your contributions are licensed under the Apache 2.0 license (see [LICENSE](LICENSE)).
+
+## Developer Certificate of Origin
+
+We respect the intellectual property rights of others and we want to make sure
+all incoming contributions are correctly attributed and licensed. A Developer
+Certificate of Origin (DCO) is a lightweight mechanism to do that. The DCO is
+a declaration attached to every commit. In the commit message of the contribution,
+the developer simply adds a `Signed-off-by` statement and thereby agrees to the DCO,
+which you can find at [DeveloperCertificate.org](http://developercertificate.org/).
+
+We require that every contribution to Valkey Swift to be signed with a DCO. We require the
+usage of known identity (such as a real or preferred name). We do not accept anonymous
+contributors nor those utilizing pseudonyms. A DCO signed commit will contain a line like:
+
+```text
+Signed-off-by: Jane Smith <[email protected]>
+```
+
+You may type this line on your own when writing your commit messages. However, if your
+user.name and user.email are set in your git configs, you can use `git commit` with `-s`
+or `--signoff` to add the `Signed-off-by` line to the end of the commit message. We also
+require revert commits to include a DCO.
+
+If you're contributing code to the Valkey Swift project in any other form, including
+sending a code fragment or patch via private email or public discussion groups,
+you need to ensure that the contribution is in accordance with the DCO.
+
+## Contributor Conduct
+All contributors are expected to adhere to the project's [Code of Conduct](CODE_OF_CONDUCT.md).
+
+## Submitting a bug or issue
+
+Please ensure to include the following in your bug report
+- A concise description of the issue, what happened and what you expected.
+- Simple reproduction steps
+- Version of the library you are using
+- Contextual information (Swift version, OS version, Valkey version, etc)
+
+## Submitting a Pull Request
+
+Please ensure to include the following in your Pull Request
+- A description of what you are trying to do. What the PR provides to the library, additional functionality, fixing a bug etc
+- A description of the code changes
+- Documentation on how these changes are being tested
+- Additional tests to show your code working and to ensure future changes don't break your code.
+
+Please keep your PRs to a minimal number of changes. If a PR is large try to split it up into smaller PRs. Don't move code around unnecessarily it makes comparing old with new very hard.
+
+The main development branch of the repository is  `main`.
+
+## Formatting
+
+We use [Apple's swift-format](https://github.com/swiftlang/swift-format) for formatting code. PRs will not be accepted if they haven't be formatted.