refactor: extract all tests & add typings for several parts

[Lodin]

In this PR I've done the following things:

• Move all tests from HTML to JS (in the form of untyped TS files).
• Reconsider approach for typings and add them for the following parts:
  • generateURL,
  • matchPath,
  • matchRoute,
  • resolver,
  • resolveRoute.

[platosha]

closing in favor of #886