Improve documentation

[curtisy1]

The current documentation is manually crafted at the gh-pages branch. While this is a good start and it's mostly still up to date, it would be a good idea to make use of the Typescript types we now have to auto-generate our docs.

---

Related issues

• https://github.com/perliedman/leaflet-routing-machine/issues/189
• https://github.com/perliedman/leaflet-routing-machine/issues/601
• https://github.com/perliedman/leaflet-routing-machine/issues/545
• https://github.com/perliedman/leaflet-routing-machine/issues/212

---

TODOs for this

• [x] Decide on a documentation framework
  • https://typedoc.org/
  • Are there any other alternatives?
• [x] Try setting up an instance
• [x] Add docs to every function and type

[curtisy1]

New documentation for the current development status is available under https://www.liedman.net/leaflet-routing-machine/docs/ Once v4 transitions to a beta release, I'll also add it to the Readme