Provide ULID#patterns instead of ULID#pattern and ULID#strict_pattern

[kachick]

I applied ULID#pattern and ULID#strict_pattern in #35.

But related Regexp might be many patterns.

• To cover Provide special parser for original Crockford's base32 possibility #78 and Should accept O, o, I, i, L, l, and - in the parser? #57
• Compatible with other tools (e.g. Visual Studio Code)
• And might be updated in future...

So providing it as collection as a Hash might be better, I think 🤔

Then considering cache strategy for them. Keeping Hash in all instance and compiles Regexp in freezing sounds needless and heavy.... They simply returns new Hash[Symbol, Regexp] when called the methods looks reasonable.