luci: include formality checks to CONTRIBUTING.md

luci: include formality checks to CONTRIBUTING.md

As a new person to contributing on GitHub,
I noticed the CONTRIBUTING.md missing
some important information that I would not
have known until I tried my first pull request,
such as the character limits and email
requirements. I've seen others also get
tripped up by this too, as they also were not
aware until afterwards. So, I have tried to
include the common ones into the
Contributing Guidelines, along with some
minor capitalisation updates for consistency.

Will also update the Pull Request template
to achieve the same goal as well.

Signed-off-by: Joshua Criss <redacted>