Issue #3446601 by ptmkenny: Add README.md

README.md

+# Firebase PHP
+
+This module integrates [kreait/firebase-php](https://github.com/kreait/firebase-php) as a Drupal service.
+
+kreait/firebase-php is an unofficial implementation of the Google Firebase Admin SDK for PHP.
+
+This module is a community implementation and not affiliated with the kreait/firebase-php project. In other words, it is an unofficial implementation of an unofficial implementation. :)
+
+This is a developer module and you will need to write code for it to be useful.
+
+See the [kreait/firebase-php documentation](https://firebase-php.readthedocs.io/en/).
+
+For a full description of the module, visit the
+[project page](https://www.drupal.org/project/firebase_php).
+
+Submit bug reports and feature suggestions, or track changes in the
+[issue queue](https://www.drupal.org/project/issues/firebase_php).
+
+
+## Warning
+
+This is an API module, but the module is not finalized. It could change at any time.
+
+If you want stability, extend FirebasePhpMessagingServiceInterface and use the $messaging service from kreait.
+
+
+## Update Policy
+
+kreait/firebase-php is a fast-moving library. There is a major release nearly every year, and only the most recent version is supported.
+
+So, this module will follow a similar update policy-- only the latest versions of Drupal and kreait/firebase-php will be supported.
+
+
+## Requirements
+
+This module requires no modules outside of Drupal core.
+
+
+## Installation
+
+Install as you would normally install a contributed Drupal module. For further information, see [Installing Drupal Modules](https://www.drupal.org/docs/extending-drupal/installing-drupal-modules).
+
+
+## Configuration
+
+1. Enable the module at Administration > Extend.
+1. At `/admin/config/system/firebase_php`, set the credentials path.
+
+### How to Get the Credentials File
+
+You will need to generate a private key file in JSON format.
+
+1. Open https://console.firebase.google.com/project/_/settings/serviceaccounts/adminsdk.
+1. Select the project.
+1. Click Generate New Private Key.
+1. Confirm by clicking Generate Key.
+1. Store the JSON file, which contains the key, in the private files directory (outside the webroot).
+
+**Do NOT commit the key to your repository.**
+
+If your private files directory is inside your webroot, move it outside your webroot. (If your host doesn't let you do this, get a new host.)
+
+
+## FAQ (optional)
+
+**Q: How can I send a test message?**
+
+**A:** Go to `admin/config/system/firebase_php/test`.
+
+
+## Maintainers
+
+- Patrick Kenny - [ptmkenny](https://www.drupal.org/u/ptmkenny)