WIP: Improve package upload category select

[MythicManiac]

Allow selection of categories for all communities a package will be submitted to instead of just the currently active community.

TODO:

• Implement a composite input for react-hook-form which aggregates all category selections into one field.
• Backend changes allowing for multi-community category selections.

[MythicManiac]

Current state can be seen here: https://streamable.com/bz8ubk

[codecov[bot]]

Codecov Report

Merging #653 (7e25dec) into master (dc389f8) will increase coverage by 0.11%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #653      +/-   ##
==========================================
+ Coverage   89.96%   90.08%   +0.11%     
==========================================
  Files         173      174       +1     
  Lines        5592     5628      +36     
  Branches      590      599       +9     
==========================================
+ Hits         5031     5070      +39     
+ Misses        478      477       -1     
+ Partials       83       81       -2     

Impacted Files	Coverage Δ
...rstore/repository/api/experimental/views/submit.py	91.48% <ø> (+4.25%)	:arrow_up:
django/thunderstore/community/factories.py	100.00% <100.00%> (ø)
...re/repository/api/experimental/serializers/main.py	98.24% <100.00%> (+0.01%)	:arrow_up:
django/thunderstore/repository/package_upload.py	81.65% <100.00%> (+1.84%)	:arrow_up:
...o/thunderstore/repository/validation/categories.py	100.00% <100.00%> (ø)

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