add type interference to plainToClass / plainToInstance

[luukvhoudt]

Description

Adds type-safe object literals to plainToClass / plainToInstance.

Untested but made this proof of concept.

declare function plainToClass<T>(cls: ClassConstructor<T>, plain: T): T;

class Foo {
    name: string = 'Hello';
}

const foo = plainToClass(Foo, {
    name: 'Bar',
    invalid: 'propName',
})

Checklist

• the pull request title describes what this PR does (not a vague title like Update index.md)
• the pull request targets the default branch of the repository (develop)
• the code follows the established code style of the repository
  • npm run prettier:check passes
  • npm run lint:check passes
• tests are added for the changes I made (if any source code was modified)
• documentation added or updated
• I have run the project locally and verified that there are no errors

Fixes

Fixes #503