Type defs for custom validation, fixes.

[FFKL]

Hello! I've improve some type definitions.

• CompilationRule, Context, CheckerFunction, CompilationFunction for custom rule definitions (directly in schema or by add method).
• RuleCustomInline upd: I think, generic isn't necesssary. Input type for validation - unknown.
• ValidationSchema fix: ability to use of root-level schema fields. For example - min: 1
• ValidationError fix: type changed to message name, message - string for custom message
• compile, validate methods fix: now it can be any type - not only object.

[coveralls]

Coverage remained the same at 100.0% when pulling c4cb8a0 on FFKL:type-def-upd into 5a699b9 on icebob:master.

[FFKL]

@icebob in source code i found sanitized property for validation object - { sanitized: boolean, source: string}. What is it used for?

[icebob]

sanitized & source are used internally only.

[icebob]

@akazakou could you review, plz?

[akazakou]

@FFKL thank you for your PR. It mostly looks good to me, but I have a few questions

[akazakou]

CheckerFunction should have a generic type for value parameter.

Suggested change

	type CheckerFunction = (value: unknown, schema: ValidationSchema, path: string, parent: object | null, context: Context) => true | ValidationError[];
	type CheckerFunction<T = unknown> = (value: T, schema: ValidationSchema, path: string, parent: object | null, context: Context) => true | ValidationError[];

[FFKL]

The same case as in the previous conversation

[akazakou]

Guess it can be resolved by that comment #122 (comment)

[FFKL]

sanitized & source are used internally only.

Maybe sanitized but not source - https://github.com/icebob/fastest-validator#custom-validator

[akazakou]

@icebob @FFKL I do not have additional questions and that PR looks good to me 🚀

[icebob]

@akazakou @FFKL so can I merge?

[FFKL]

@akazakou @FFKL so can I merge?

I think - yes)

[icebob]

Thanks to both of you!