Upgrade path-to-regexp from v3 to v6

[frenzzy]

This PR continues a rewriting to TypeScript started in #166 and also upgrades path-to-regexp dependency which brings new possibilities, see changelog.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

TODO:

• [ ] Reuse common code between src/UniversalRouter.ts and src/UniversalRouterSync.ts
• [ ] Allow to redefine Route type
• [x] Add JSDoc to definitions

Closes #166 Closes #182 Closes #186

[codecov-io]

Codecov Report

Merging #183 into master will not change coverage. The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #183   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           7      3    -4     
  Lines         180    205   +25     
  Branches       53     63   +10     
=====================================
+ Hits          180    205   +25

Impacted Files	Coverage Δ
src/UniversalRouterSync.ts	100% <100%> (ø)
src/generateUrls.ts	100% <100%> (ø)
src/UniversalRouter.ts	100% <100%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 4bf7acd...ed9b3d2. Read the comment docs.