luci: improvements to pull_request_template

luci: improvements to pull_request_template

As a new person to contributing on GitHub,
I noticed the Pull Request template 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 template.

I have also prepared a layout that would
ensure a more uniform experience when
looking through Pull Requests, with expected
headings and the ability to provide the
instruction of what to put under each heading.
Minor grammar and punctuation edits as well.

If the layout is preferred as a seperate Pull
Request, let me know and I will do so.

Will also update the CONTRIBUTING.md
file to achieve the same goal as well.

Signed-off-by: Joshua Criss <redacted>