Update docs, prepare for v4.3.0 release

[lopopolo]

Release boba 4.3.0

boba is published on crates.io.

This release contains enhancements and performance optimizations. boba::decode is 35% faster than v4.2.0.

• Optimize encode for empty input by hardcoding the result. Optimize encode for empty input by hardcoding the result #135
• Minimize codebloat by moving encoder and decoder out of generic function. Minimize codebloat by moving encoder and decoder out of generic function #136
• Optimize boba::decode. Optimize boba::decode #137
• Remove bstr dependency and reimplement bits that are used in decode. Remove bstr and reimplement bits that are used in decode #138

Improvements to dev dependencies and benchmark tooling:

• Update version-sync to 0.9.3 and trim some deps from Cargo.lock. Update version-sync to 0.9.3 and trim some deps from Cargo.lock #117
• Remove comparison benches with alternate implementation. Remove comparison benches with alternate implementation #123
• Migrate benches to subcrate with criterion, remove nightly toolchain dep. Migrate benches to subcrate with criterion, remove nightly toolchain dep #134

This release also includes several code quality improvements:

• Scope encoded length to block for constructing the decode buffer. Scope encoded length to block for constructing the decode buffer #103
• Format use import statements to have groups for core + other deps. Format use import statements to have groups for core + other deps #104

This release contains improvements to documentation and build process.