Length modes

[jprochazk]

• Closes https://github.com/jprochazk/garde/issues/84

• Closes https://github.com/jprochazk/garde/issues/40

• Add a mode argument to the length rule. Currently supports:

  • simple, which is the default
  • bytes
  • chars
  • graphemes
  • utf16

• Remove byte_length

[jprochazk]

half is causing way too many issues. Don't want to bump the msrv, so I'm just going to remove the benchmarks and criterion.

[jprochazk]

Released in v0.18