Update README.md

Author: calumgrant

README.md

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 # Ruby analysis support for CodeQL
 
-Under development.
+This open-source repository contains the extractor, CodeQL libraries, and queries that power Ruby
+support in [LGTM](https://lgtm.com) and the other CodeQL products that [GitHub](https://github.com)
+makes available to its customers worldwide.
+
+It contains two major components:
+  - an extractor, written in Rust, that parses Ruby source code and converts it into a database
+    that can be queried using CodeQL.
+  - static analysis libraries and queries written in [CodeQL](https://codeql.github.com/docs/) that can be
+    used to analyze such a database to find coding mistakes or security vulnerabilities.
+
+The goal of this project is to provide comprehensive static analysis support for Ruby in CodeQL.
+
+For the queries and libraries that power CodeQL support for other languages, visit [the CodeQL
+repository](https://github.com/github/codeql).
+
+## Installation
+
+Simply clone this repository. There are no external dependencies.
+
+If you want to use the CodeQL extension for Visual Studio Code, import this repository into your VS
+Code workspace.
+
+## Usage
+
+To analyze a Ruby codebase, either use the [CodeQL command-line
+interface](https://codeql.github.com/docs/codeql-cli/) to create a database yourself, or
+download a pre-built database from [LGTM.com](https://lgtm.com/). You can then run any of the
+queries contained in this repository either on the command line or using the VS Code extension.
+
+Note that the [lgtm.com](https://github.com/github/codeql-ruby/tree/lgtm.com) branch of this
+repository corresponds to the version of the queries that is currently deployed on LGTM.com.
+The [main](https://github.com/github/codeql-ruby/tree/main) branch may contain changes that
+have not been deployed yet, so you may need to upgrade databases downloaded from [LGTM.com](https://lgtm.com) before
+running queries on them.
+
+## Contributions
+
+Contributions are welcome! Please see our [contribution guidelines](CONTRIBUTING.md) and our
+[code of conduct](CODE_OF_CONDUCT.md) for details on how to participate in our community.
+
+## Licensing
+
+The code in this repository is licensed under the [MIT license](LICENSE).
+
+## Resources
+
+- [Writing CodeQL queries](https://codeql.github.com/docs/writing-codeql-queries/)
+- [CodeQL documentation](https://codeql.github.com/docs/)
+
+# Developer information
 
 ## Building the tools from source