Add nf-core colors to rtd sphinx theme

[mashehu]

Adds sphinx to dev requirements file.

Switches based on OS/browser between light theme:

and dark theme:

[github-actions]

This PR is against the master branch ❌

• Do not close this PR
• Click Edit and change the base to dev
• This CI test will remain failed until you push a new commit

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Hi @mashehu,

It looks like this pull-request is has been made against the mashehu/tools master branch.
The master branch on nf-core repositories should always contain code from the latest release.
Because of this, PRs to master are only allowed if they come from the mashehu/tools dev branch.

You do not need to close this PR, you can change the target branch to dev by clicking the "Edit" button at the top of this page.
Note that even after this, the test will continue to show as failing until you push a new commit.

Thanks again for your contribution!

[codecov]

Codecov Report

Merging #926 (d058b1a) into dev (8648c11) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #926      +/-   ##
==========================================
- Coverage   69.58%   69.56%   -0.02%     
==========================================
  Files          34       34              
  Lines        4162     4176      +14     
==========================================
+ Hits         2896     2905       +9     
- Misses       1266     1271       +5     

Impacted Files	Coverage Δ
nf_core/modules/lint.py	62.58% <0.00%> (-0.04%)	⬇️
nf_core/lint/__init__.py	77.19% <0.00%> (+0.10%)	⬆️

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[ewels]

Love it 💚

[ewels]

Building: https://github.com/nf-core/tools/actions/runs/675597250

[ewels]

Live: https://nf-co.re/tools-docs/