Add README for the generator

Author: fabaff

credits_generator/README.md

@@ -0,0 +1,29 @@
+credits_generator
+=================
+
+This tool can be used to update the [Home Assistant's Credits page](https://home-assistant.io/developers/credits/).
+
+```bash
+$ cd credits_generator
+$ npm install
+```
+
+Set your personal GitHub access token as environmental variable.
+
+```bash
+$ export GITHUB_TOKEN=<Your GitHub access token>
+```
+
+Run the script.
+
+```bash
+$ node update_credits.js
+```
+
+Commit the changes (depending on our setup).
+
+```bash
+$ git commit ../source/developers/credits.markdown
+$ git push upstream
+```
+