docs: update project information

Author: mrholek

.github/CONTRIBUTING.md

@@ -29,7 +29,7 @@ Guidelines for bug reports:
 
 1. **Use the GitHub issue search** — check if the issue has already been reported.
 
-2. **Check if the issue has been fixed** — try to reproduce it using the latest `master` or development branch in the repository.
+2. **Check if the issue has been fixed** — try to reproduce it using the latest `main` or development branch in the repository.
 
 3. **Isolate the problem** — ideally create a [reduced test case](https://css-tricks.com/reduced-test-cases/) and a live example. [This JS Bin](http://jsbin.com/lefey/1/edit?html,output) is a helpful template.
 
@@ -96,8 +96,8 @@ included in the project:
 2. If you cloned a while ago, get the latest changes from upstream:
 
    ```bash
-   git checkout master
-   git pull upstream master
+   git checkout main
+   git pull upstream main
    ```
 
 3. Create a new topic branch (off the main project development branch) to
@@ -116,7 +116,7 @@ included in the project:
 5. Locally merge (or rebase) the upstream development branch into your topic branch:
 
    ```bash
-   git pull [--rebase] upstream master
+   git pull [--rebase] upstream main
    ```
 
 6. Push your topic branch up to your fork:
@@ -125,7 +125,7 @@ included in the project:
    git push origin <topic-branch-name>
    ```
 
-7. [Open a Pull Request](https://help.github.com/articles/using-pull-requests/) with a clear title and description against the `master` branch.
+7. [Open a Pull Request](https://help.github.com/articles/using-pull-requests/) with a clear title and description against the `main` branch.
 
 **IMPORTANT**: By submitting a patch, you agree to allow the project owners to license your work under the terms of the [MIT License](LICENSE).
 

.github/ISSUE_TEMPLATE.md

@@ -2,7 +2,7 @@ Before opening an issue:
 
 - [Search for duplicate or closed issues](https://github.com/coreui/coreui-free-bootstrap-admin-template/issues?utf8=%E2%9C%93&q=is%3Aissue)
 - Prepare a [reduced test case](https://css-tricks.com/reduced-test-cases/) for any bugs
-- Read the [contributing guidelines](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/master/CONTRIBUTING.md)
+- Read the [contributing guidelines](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/main/.github/CONTRIBUTING.md)
 
 When asking general "how to" questions:
 

README.md

@@ -135,9 +135,9 @@ The documentation for the CoreUI Free Bootstrap Admin Template is hosted at our
 
 ## Contributing
 
-Please read through our [contributing guidelines](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/master/CONTRIBUTING.md). Included are directions for opening issues, coding standards, and notes on development.
+Please read through our [contributing guidelines](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/main/.github/CONTRIBUTING.md). Included are directions for opening issues, coding standards, and notes on development.
 
-Editor preferences are available in the [editor config](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/master/.editorconfig) for easy use in common text editors. Read more and download plugins at <http://editorconfig.org>.
+Editor preferences are available in the [editor config](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/main/.editorconfig) for easy use in common text editors. Read more and download plugins at <http://editorconfig.org>.
 
 ## Versioning
 
@@ -171,7 +171,7 @@ Some of projects created by community but not maintained by CoreUI team.
 
 ## Copyright and license
 
-copyright 2019 creativeLabs Łukasz Holeczek. Code released under [the MIT license](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/master/LICENSE).
+copyright 2021 creativeLabs Łukasz Holeczek. Code released under [the MIT license](https://github.com/coreui/coreui-free-bootstrap-admin-template/blob/main/LICENSE).
 There is only one limitation you can't can’t re-distribute the CoreUI as stock. You can’t do this if you modify the CoreUI. In past we faced some problems with persons who tried to sell CoreUI based templates.
 
 ## Support CoreUI Development