:memo: Add more Emoji to the contributing guide

Suggest Emoji for:
 - Fixing something on Mac OS
 - Fixing a bug
 - Burning whitespace
 - Fixing the CI build
 - Adding tests
 - Refactoring
 - Security
Use :apple: for Mac OS specific bugs
Use :fire: emoji for general deleting of code
Remove :recycle: from the emoji in CONTRIBUTING.md
Change security emoji to :lock:
Merge pull request #2198 from hkdobrev/commits-emoji

Add more Emoji to the contributing guide