Add StyleCI configuration file (.styleci.yml)

[patrickdaze]

Add StyleCI to automatically clean up code and pull requests.

Once this PR is merged I recommend the following:

1. Login to https://styleci.io/ and connect it to thomasedwards/bulmasearch
2. Configure the repo on StyleCI (something like https://github.styleci.io/repos/<repo_id>/settings):
   1. Remove any content in "Configure Repo" textarea and click Save Configuration. This will allow StyleCI to use the .styleci.yml file
   2. In Automation Level, select your desired option. Maybe "Send fixes as pull requests on demand only" or "Automatically send fixes as pull requests only"
   3. You may or may not want to disable "Fix PR Commit CI Skipping" and "Direct/Merge Commit CI Skipping"