Suggestion: add "xx" keyword

[CAD97]

I nearly couldn't find this crate

[xpe]

As of today (2023-09-05), I had better luck with https://lib.rs than https://crates.io:

lib.rs

Searching lib.rs for "xxhash" gives these top two results, which are exactly what I hoped to find:

• xxhash-rust xxhash v0.8.6 486K #hash #xxhash #xxh3 #hasher
• twox-hash XXHash and XXH3 algorithms v1.6.3 1.0M #hash #hasher #xxhash #xxh3

crates.io

In comparison, searching crates.io for "xxhash" gives something like the following:

• xxhash v0.0.8
• xxhash-rust v0.8.6
• xxhash-c v0.8.2
• xxhash-c-sys v0.8.4
• xxhash-sys v0.1.0
• xxhrs v2.0.0
• twox-hash v1.6.3
• twox-hash-cli v1.0.0