feat: add dark theme feature

[AlanSyue]

I'd like to add the feature which can change light or dark theme.

I use this repo to implement this feature
https://github.com/karl-run/react-dark-theme

Hope this feature can be merged, thank you

[wojtekmaj]

Hi @AlanSyue! Thanks, I think it's an excellent idea. I worked on it a little more and implemented this in #71. Most notably, dependency on react-dark-theme was removed - there was really no need to have it, and this added a bit of bloat to our bundle.

You'll be co-authored :) Thanks!

[AlanSyue]

@wojtekmaj Thanks!

[AlanSyue]

@wojtekmaj
I've participated in Hacktoberfest event, could you please added the label hacktoberfest-accepted to this PR？
Thanks a lot！

[wojtekmaj]

There you go :)