Update contributing guide (add TOC, return to work, debugging)

[reshamas]

PR Overview

Type of contribution

• [ ] Code
• [x] Documentation

Reference: Issue or Pull Request (PR)

Towards #361 Towards #393

Description of Changes

• consistently use "Events Board"
• add Table of Contents to Contributing file
• add sub-section in Contributing for "return to work"
• add sub-section in Contributing for "debugging"

Before and After for UI Updates

<-- You should have 2 images minimum, for desktop, 4 for mobile and desktop combined -->

Before:

After:

For PR Reviewer

• [ ] Does this file change the yarn.lock, package.json or package-lock.json file? If so, why?
• [ ] If this pr contains mobile and desktop changes, did you test on IphoneXr and desktop views?
• [ ] Does this file match the related tickets linked figma file, or does it pass the visual smell test?
• [ ] If this file contains javascript, does the javascript pass the smell test?
• [ ] If you don't feel super confident in your review, did you assign someone more senior to double check?