feat: add helper responses module

[onerandomusername]

picked from GH-69

depends on #68

[onerandomusername]

Oh I'll just write tests for this too, one minute.

[codecov[bot]]

Codecov Report

Merging #88 (bbef578) into main (9c5d9dd) will increase coverage by 1.86%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #88      +/-   ##
==========================================
+ Coverage   68.75%   70.62%   +1.86%     
==========================================
  Files          30       32       +2     
  Lines        1498     1593      +95     
  Branches      183      190       +7     
==========================================
+ Hits         1030     1125      +95     
  Misses        437      437              
  Partials       31       31              

Impacted Files	Coverage Δ
modmail/extensions/utils/error_handler.py	30.64% <100.00%> (+0.56%)	:arrow_up:
modmail/utils/responses.py	100.00% <100.00%> (ø)
tests/modmail/utils/test_responses.py	100.00% <100.00%> (ø)

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[dpulls[bot]]

:tada: All dependencies have been resolved !