docs: document repository

Author: Greg Bowler

.github/FUNDING.yml

@@ -0,0 +1,2 @@
+# These are supported funding model platforms
+github: [g105b]

README.md

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 Run your Behat tests in your Github Actions.
 ============================================
 
-Behat is an open source Behavior Driven Development framework for PHP 5.3+. What’s behavior driven development, you ask? It’s a way to develop software through a constant communication with stakeholders in form of examples; examples of how this software should help them, and you, to achieve your goals.
+Behat is an open source Behavior Driven Development framework. What’s behavior driven development, you ask? It's a way to develop software through a constant communication with stakeholders in form of examples; examples of how this software should help them, and you, to achieve your goals.
+
+> Given I am on "https://github.com/php-actions/behat"
+> When I press "Star this repository"
+> Then I should be a stargazer of "php-actions/behat"
+> And I should see "Unstar this repository"
 
 Usage
 -----
 
-// TODO: WIP
+Create your Github Workflow configuration in `.github/workflows/ci.yml` or similar.
+
+```yml
+name: CI
+
+on: [push]
+
+jobs:
+  build-test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: php-actions/composer@v3
+      - uses: php-actions/behat@v1
+      # ... then your own project steps ...
+```
+
+### Version numbers
+
+This action is released with semantic version numbers, but also tagged to the latest major release's tag always points to the latest release within the matching major version.
+
+Please feel free to use `uses: php-actions/behat@v1` to always run the latest version of v1, or `uses: php-actions/behat@v1.0.1` to specify an exact release.
+
+Example
+-------
+
+We've put together an extremely simple example application that uses `php-actions/behat`. Check it out here: https://github.com/php-actions/example-behat.
+
+Inputs
+------
+
+The following configuration options are available:
+
++ ???
+
+The syntax for passing in custom input is the following: 
+
+```yml
+...
+jobs:
+  behat:
+
+    ...
+
+    - name: Behat tests
+      uses: php-actions/behat@v1
+      with:
+        config: path/to/behat.yml
+        memory_limit: 256M
+```
+
+If you require other configurations of Behat, please request them in the [GitHub issue tracker][issues].
+
+PHP and Behat versions
+----------------------
+
+It's possible to run any version of Behaty under any version of PHP, with any PHP extensions you require. This is configured with the following inputs:
+
++ `version` - the version number of Behat to run, e.g. `3` or `3.11.0` (default: latest)
++ `php_version` - the version number of PHP to use, e.g. `7.4` (default: latest)
++ `php_extensions` - a space-separated list of extensions to install using [php-build][php-build], e.g. `xdebug mbstring` (default: N/A)
+
+Please note the version number specified within your Action configuration must match your `composer.json` major version number. For example, if your composer.json requires `behat/behat 3.11.0`, you must use the version: `3.11.0` input, as major versions of PHPBehat are incompatible with each other.
+
+If you require a specific version that is not compatible with GitHub Actions for some reason, please make a request in the [GitHub issue tracker][issues].
+
+***
+
+If you found this repository helpful, please consider [sponsoring the developer][sponsor].
+
+[issues]: https://github.com/php-actions/behat/issues
+[php-build]: https://github.com/php-actions/php-build
+[sponsor]: https://github.com/sponsors/g105b