feat(CDN): animated banners

[iShibi]

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

Both user and guild banners can be animated now:

• Document animated guild banners discord/discord-api-docs#3948

Status and versioning classification:

[codecov]

Codecov Report

Merging #73 (9236a0a) into main (8ba5374) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main      #73   +/-   ##
=======================================
  Coverage   88.91%   88.91%           
=======================================
  Files           9        9           
  Lines        1489     1489           
  Branches      155      155           
=======================================
  Hits         1324     1324           
  Misses         12       12           
  Partials      153      153           

Impacted Files	Coverage Δ
packages/rest/src/lib/CDN.ts	88.83% <100.00%> (ø)

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[kyranet]

You have merge conflicts.