feat(CDN): add sticker endpoints

[vaporoxx]

Please describe the changes this PR makes and why it should be merged:

This adds the CDN endpoints for stickers and sticker pack banners. (Reference)

Status and versioning classification:

• I know how to update typings and have done so
• This PR changes the library's interface (methods or parameters added)

[codecov]

Codecov Report

Merging #60 (96c9e27) into main (c4b2803) will increase coverage by 0.28%.
The diff coverage is 90.69%.

@@            Coverage Diff             @@
##             main      #60      +/-   ##
==========================================
+ Coverage   85.80%   86.08%   +0.28%     
==========================================
  Files           8        8              
  Lines        1000     1035      +35     
  Branches      100      102       +2     
==========================================
+ Hits          858      891      +33     
  Misses         42       42              
- Partials      100      102       +2     

Impacted Files	Coverage Δ
packages/rest/src/lib/CDN.ts	87.83% <90.24%> (+1.29%)	⬆️
packages/rest/src/lib/utils/constants.ts	100.00% <100.00%> (ø)

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