(GitHub Dark Default and GitHub Dark Dimmed) disabled extensions are difficult to distinguish #159

Using the extension v4.0.2 with VSCode 1.55.2 on windows 10.

I've noticed that when using the GitHub Dark Default and GitHub Dark Dimmed themes,
the disabled extensions are difficult to distinguish.

Screenshot comparison:
Light+ (default light) <-- ok
Dark+ (default dark) <-- ok

GitHub Dark Default <-- difficult to distinguish
GitHub Dark Dimmed <-- almost indistinguishable

I'm aware that you have released these GitHub.com themes just a few days ago, I just wanted to mention this to you.

Thank you