Add basic missing constraints

[nesk]

CharSequence:

• hasLengthEqualTo, hasLengthNotEqualTo
• isBlank, isNotBlank
• regex with isMatching, isNotMatching

All collections:

• isEmpty, isNotEmpty
• hasSizeEqualTo, hasSizeNotEqualTo
• isContaining, isNotContaining

[dave08]

Maybe also support for kotlinX.datetime (if it doesn't already exist?). For those using it, those types are also considered pretty much basic... but I guess it would be in another module...

[nesk]

@dave08 This is already in the roadmap 😉