Add Panel Support for GitHub

[jdkuki]

Description

Feature Request:
Add functionality to tip users on GitHub via panel

Steps to Reproduce

1. Enroll in rewards
2. Visit user profile page on GitHub
3. Click Brave Rewards BAT Icon to open panel
4. Text on panel should appear "(username) on GitHub"

Actual result:

N/A

Expected result:

Reproduces how often:

n/a

Brave version (brave://version info)

n/a

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:

[GeetaSarvadnya]

Verification passed on

Brave	0.69.124 Chromium: 76.0.3809.132 (Official Build) (64-bit)
Revision	fd1acc410994a7a68ac25bc77513d443f3130860-refs/branch-heads/3809@{#1035}
OS	Windows 10 OS Version 1803 (Build 17134.523)

• Verified the STR mentioned in the description

• Logged Username is NOT displayed in BR panel when GH profile name is empty #5904

Verified passed with

Brave	0.69.124 Chromium: 76.0.3809.132 (Official Build) (64-bit)
Revision	fd1acc410994a7a68ac25bc77513d443f3130860-refs/branch-heads/3809@{#1035}
OS	Mac OS X

• Verified the STR mentioned in the description for verified, connected, and non-verified publishers
• Encountered Username is NOT displayed in BR panel when GH profile name is empty #5904

Verification passed on

Brave	0.69.124 Chromium: 76.0.3809.132 (Official Build) (64-bit)
Revision	fd1acc410994a7a68ac25bc77513d443f3130860-refs/branch-heads/3809@{#1035}
OS	Ubuntu 18.04 LTS