Ideas for better language handling

[curtisy1]

There are lots of issues and questions about how to customize/adjust the languages. Generally I believe it's a good idea to separate the localization logic from the core library going forward, so everyone can add their own translations or import one of the existing defaults.

A few benefits of this are:

• Reduced bundle size, since we don't have all of osrm-text-instructions anymore. This would then be opt-in
• Dynamic loading of only required languages instead of all languages in a single file/directory

To achieve this, we could pass the localization object itself to the routing control and let the user handle any previous setup. If not language is provided, we fall back to English. For this, a standalone package will be needed.

Since this would imply a breaking change, it could only land in a v4 together with the Typescript rewrite and the itinerary decoupling

[curtisy1]

I decided against splitting the project into multiple parts for now since maintaining a monorepo of sorts would not be feasible at this stage. I'd much rather focus on getting a v4.0 ready for now and maybe roll that out simultaneously.