Super Cache: support Brotli compression

[ahmed-sigmalux]

It would be nice if support for Brotli compression were added to the plugin.

[donnchawp]

I await your patch including code, settings and documentation. :)

[stathis]

I am too interested in Brotli pre-compressed files. Would be a great feature to have.

[stathis]

Here you go.
Automattic/wp-super-cache#720

[joshlucio05]

When are we getting this feature?

[bobmatyas]

Brotli support raised here:

https://wordpress.org/support/topic/enable-brotli-static-via-a-hook/

Also in #31724.