Updates To .Gitignore

Proposal
=======

This is a proposed change to how themosis tracks files for Wordpress builds. The intended goal of this is to keep git repositories at a minimum size and protect sensitive information from being committed to the version control system.

**Vendor Files**
The `vendor` directory is not necessary to track as it is managed by `composer.json` already and will only bloat git repos. 

**Dotenv Files**
The `.env` files are meant to keep valuable credentials out of version control systems. Having `.env.example.php` will inform the user of how they need to structure the `.env` file but will not allow sensitive files to be committed. 

**Wordpress Plugins & Uploads**
The plugins for Wordpress in the configuration Themosis is in can be managed through composer with `wpackagist`. There is no reason to track these in the current setup. In a local/staging/production paradigm there is typically no reason to track the `uploads` folder as well because the production uploads will not be overwritten in deployment. 

All of this should be omitted from version control to keep repos at a conservative size.

**Final**
Thanks for your time. I love Themosis so far. It's done very well. :+1: 
Should this be `!/htdocs/content/themes/*`?