Replace key hardcoded parameters with config files

Currently settings such as the tags associated with paths on which cycling is forbidden are hard coded in `.rs` files:

https://github.com/Urban-Analytics-Technology-Platform/od2net/blob/b3fb828f1a9f213b30d62b3231910e4b6da4f151/lts/src/allowed.rs#L31-L38

Would it be possible to replace such settings with config files in `json` for easier editing and less Rust code reading? Aligns with the aim set out in #28 to make this more accessible (and in this case configurable) for others.

Use case: places like Norway and I believe Japan where cycling on footpaths is allowed, or for uses where we want to route cycling on a wider part of the network to inform investment decisions.