feat: implement convert unit command

[HeadTriXz]

Adds a new command that allows users to easily convert units.

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (2e2f933) 98.86% compared to head (79c40cc) 98.85%.

Files	Patch %	Lines
...odules/general/commands/chatinput/convert/index.ts	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #99      +/-   ##
==========================================
- Coverage   98.86%   98.85%   -0.01%     
==========================================
  Files         200      201       +1     
  Lines       21732    21938     +206     
  Branches     2384     2408      +24     
==========================================
+ Hits        21485    21687     +202     
- Misses        245      249       +4     
  Partials        2        2              

Flag	Coverage Δ
barry	98.59% <97.58%> (-0.01%)	⬇️
core	99.92% <ø> (ø)
logger	100.00% <ø> (ø)

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