bitap algorithm implemented along with pz_error updates

[Dhivakar-collab]

No description provided.

[san-rizz-777]

Change the implementation to fuzzy search rather than exact and return type to "std::optional", consider using "pz_cxx_std.hpp" in include directory rather than "vector" or "cstdin".

[san-rizz-777]

1. Off-by-one bug: 1ULL << m should be 1ULL << (m-1), currently misses valid matches.(ex-> pattern="a" and text="a", m=1, doesn't matches trace it.)
2. max_errors >= m warns but doesn't return keeps running with bad config.(missing return here in if block)
3. Pass word/pattern by const&, not by value.
4. std::vector R heap-allocates every call, use fixed std::array<st64,64>.
5. Rename "word" to "text", it reads like the pattern.
6. Use std::variant for return type.