Add support for tipping Github users (Github inline tipping)

[jdkuki]

Description

Feature request:
GitHub inline tipping should be enabled in several aspects of the GitHub website.
See screenshots/below specification document for affected ares.

Supported Areas:

https://github.com/<user>/<repository>/issues/<issue_number>
https://github.com/<user>/<repository>/pull/<pr_number>
https://github.com/<user>?tab=stars
https://github.com/<user>/<repository>/commits/<branch_name>
https://github.com/orgs/<org>/people
https://github.com/orgs/<org>/teams/<team_name>/members
https://gist.github.com/<user>/<gist_number>

Steps to Reproduce

1. Join Rewards
2. Browse to user profile (ex. github.com/jdkuki)
3. Click "stars tab"
4. Tip buttons should appear next to star button
5. Click tip button
6. Tip banner should appear with text "(profile_name)* on GitHub". Name should correspond to creator
   of starred item
7. Select tip amount and send
8. Transaction should show up in pending contributions or balance should update according to
   publisher verification status
9. Navigate to brave://rewards
10. Under tips settings, uncheck "GitHub"
11. Open pages with injected tip buttons should see tip buttons disappear.

*If profile name is not set, banner will display username handle instead

Screenshots

Please reference specification for exact appearance. Few examples:
PR

Issues

Commits

Actual result:

n/a

Expected result:

Reproduces how often:

Brave version (brave://version info)

Version/Channel Information:

• Can you reproduce this issue with the current release?
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the dev channel?
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information: