restore Binary class
major cleanups, drop paragonie/constant_time_encoding dependency
update links to sr.ht
small comment changes
lots of cleanups

- make static code analyzers happy
- move header check until after the signature has been verified
- remove public `Jwt::setDateTime()`, was only used for testing and nobody was
  supposed to use it anyway, if they do/did that is a security issue, and their
  code MUST break
- actual algorithm classes have now a `getAlgorithm()` method exposing the
  JWT algorithm instead of a `const`
format psalm.xml.dist
add Phan config, update psalm config
add Summary/Description
switch to paragonie/sodium_compat for composer installs
update version section
add version table
also benchmark signature validation