docs(internal): Document release pipeline (#11141)
### Description
The release pipeline is fairly complicated. Documenting in it its
entirety is a good idea.
### Testing Instructions
Give it a read and see what you think.
<sub>CLOSES TURBO-4967</sub>
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Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com>
