Add io.streams.compress.Deflate and register it in algorithms

[thekid]

See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Encoding, where this is listed as one of the example values

[thekid]

This is dangerous as deflate in HTTP context is a misnomer and refers to zlib rather than raw deflate, see https://www.php.net/manual/de/function.gzdeflate.php#usernotes and https://stackoverflow.com/a/1579506:

• HTTP gzip is the GZIP file format.
• HTTP deflate is actually the ZLIB data format. (But some clients do also accept the actual DEFLATE data format for deflate.)

Maybe we should add a separate method named Compression::http() to separate the lookup by tokens used in content negotiation vs. common names:

$httpDeflate= Compression::http('deflate');
$rawDeflate= Compression::named('deflate');

Alternatively, we would register our (raw deflate) implementation as raw-deflate.

[thekid]

However, deflate doesn't seem to be commonly used anymore, neither MDN, nor Google, nor GitHub would even react to Accept-Encoding: deflate, simply producing uncompressed output.

Historically, "deflate" was problematic because early Microsoft IIS servers would send raw deflate data instead of zlib data (see https://stackoverflow.com/a/9186091/1218408). To work around that, it became common to just use gzip.

Source: https://stackoverflow.com/questions/7243705/what-is-the-advantage-of-gzip-vs-deflate-compression

It might be clever to not merge this pull request at all, while continuing to provide the stream implementations should people need them.