Updates docs for open source and Alley developers

### Description of the documentation inaccuracy

- Update READMEs on this project as well as https://github.com/alleyinteractive/create-wordpress-plugin and https://github.com/alleyinteractive/create-wordpress-theme
- Update internal Alley Documentation

here's the command to create a theme: `composer create-project alleyinteractive/create-wordpress-theme themes/{slug}`
and the command to create a plugin `composer create-project alleyinteractive/create-wordpress-plugin plugins/{slug}`

### Additional Information

_No response_