Dark mode

[jasonyess]

Added dark mode using prefers-color-scheme css media query. Dark mode is toggled on/off based on the user's system theme, which can also be overridden with js by modifying the stylesheets' css rules

There may be a few redundant css declarations in the media queries (but it works and i don't want to break anything)

Resolves #93

License Acceptance

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 29.57%. Comparing base (a945624) to head (fd295da).
Report is 12 commits behind head on master.

Files with missing lines	Patch %	Lines
...te-demonlist-pages/src/account/list_integration.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #180      +/-   ##
==========================================
+ Coverage   29.35%   29.57%   +0.21%     
==========================================
  Files         117      116       -1     
  Lines        8321     8314       -7     
==========================================
+ Hits         2443     2459      +16     
+ Misses       5878     5855      -23     

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[stadust]

Hi @jasonyess,
thanks for this PR! I'm focusing a lot on the oauth stuff right now, but I'll have a look at this right after!