Allow constructing a finder via a const fn

[Dr-Emann]

It would be really nice if we could just have

const XML3: BytesConst = jetscii::bytes![0, 5, 15];

This requires every implementation to be constructible at compile time, even for simd algorithms which may not have support for the current CPU. This is currently the case for the sse4.2 simd implementation as well as the aarch64 implementation I'm working on (#61), but it would mean we couldn't e.g. use the teddy searcher from aho_corasick

Related to #59, but for Bytes/AsciiChars