Implement unic-ucd-case and unic-case

[behnam]

Char Properties:

• Lowercase
• Uppercase
• Cased
• Case_Ignorable
• Changes_When_*

Implements case-folding algorithms:
(TBD.)

Related crates:

• https://crates.io/crates/case
• https://crates.io/crates/heck
• https://crates.io/crates/casing
• https://crates.io/crates/ident_case
• https://crates.io/crates/unicase
• https://crates.io/crates/changecase
• https://crates.io/crates/titlecase

[behnam]

#157 has a basic implementation for the character properties listed here.

However, based on their definition, we can reduce the number of tables we store and compose the result from other properties (GC) or other tables. When doing so, we can move the tables auto-created here to case/tests/tables/ and only use them to match the behavior of the composition with direct lookup.

[recmo]

I have a need for standards conformant culture-neutral case invariant comparison. I think this may be simple enough to contribute as a PR to unic. Where can I find the canonical specificiation of the folding algorithms and any other information I may need to implement this?