doc: clarify code of conduct reporting

doc: clarify code of conduct reporting

Clarifies the code of conduct by making the following changes:

- Adds section headings to make it easier to quickly parse.
- Adds easy to find contact information.
- Adds link to TSC moderation policies.
- Moves attribution to the bottom of the page.

PR-URL: https://github.com/nodejs/node/pull/5107
Reviewed-By: Myles Borins <mborins@us.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Kat Marchán <kzm@sykosomatic.org>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>