zstd-stream compression support

[valzargaming]

https://discord.com/developers/docs/events/gateway#zstdstream

[valzargaming]

zstd compression is not supported by PHP out of the box. An extension is currently being maintained by kjdev/php-ext-zstd and we should consider it as a viable option.

[alexandre433]

In my opinion, we shouldn't use any types of compressions with a library that doesn't have a v1 released.
We either use one of the top 5 of that list or top 3, but one that is already supported with php, if that's the cast.
Else we go to the "worst" there is but that is supported.

There can be a branch with that integration only, but in "master" I 100% disagree.

[valzargaming]

The currently-available transport compression options are zlib-stream and zstd-stream. Only zlib-stream is implemented at this time and will remain the default for the current major version of DiscordPHP.