Add JSDoc comments on the TextureUvs properties

[mofnire]

Description of change

The PIXI.TextureUvs properties such as x0 are missing in the type declaration file. I thought this might be intentional. If so, I'm sorry for bothering you :(. However, they were in the PixiJS v4 type declaration file. So I thought this might be not. This PR adds JSDoc comments on the TextureUvs properties.

I omit the property TextureUvs#uvsFloat32 on purpose.
It looks too internal to me.

Pre-Merge Checklist

• Documentation is changed or added
• Lint process passed (npm run lint)

[codecov-io]

Codecov Report

Merging #5828 into dev will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              dev    #5828   +/-   ##
=======================================
  Coverage   70.57%   70.57%           
=======================================
  Files         205      205           
  Lines       10396    10396           
=======================================
  Hits         7337     7337           
  Misses       3059     3059

Impacted Files	Coverage Δ
packages/core/src/textures/TextureUvs.js	100% <ø> (ø)	⬆️

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