Poor support with github dark themes

[blakeboll]

Bug Information

• Site: github
• Theme: none
• URL: https://github.com/liorgrossman/darkness/issues/new?assignees=&labels=&template=bug_report.md
• Darkness Version: 2.0.26 Pro
• Browser: Chrome 91.0.4472.164
• Operating System: Mac OS X 10_15_7
• Resolution: 2560x1440
• Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.164 Safari/537.36

Bug Description
Github offers many in site dark mode options. When one of Github's dark mode options is enabled and a theme is chosen from the Darkness Pro extension you get some sort of double color inversion on some elements.

Screenshots

• For example the title input header in the bug report, and the Attach files dropzone at the bottom of the issue textarea.
  
• Github projects columns.