Make hash configurable

[SebCorbin]

Motivation

Hash option is a boolean, if we set it, we can't use location.hash for anything else other than the mapbox hash. It would be nice to implement a query parameter style, if defined, like myurl.org/mymap#map=10.37/14.589/-61.0225&config=myotheroptions.
This is useful for permalinks for application containing a configurable map of anything else actually.

Design Alternatives

Add an optional (to prevent breaking change) hashName option, that if defined, make the hash a query parameter-styled string.

Implementation

Add and document this option, modify ui/hash.js so that it replaces (if defined), only the hashName part of the map.

[asheemmamoowala]

@SebCorbin Thanks for the proposal. Would you be interested in implementing it as well? The changes should be limited to https://github.com/mapbox/mapbox-gl-js/blob/master/src/ui/hash.js and fairly isolated to test.

[SebCorbin]

Sure, I have a PR in progress, I think I'll drop the hashName in favor of a hash option that can be boolean or string. I see that you support IE11, so I may not use URLSearchParams, right?

[andrewharvey]

Related to #7725. I like this approach to make it more flexible and let the developer choose the name they want to use.

[JesseWeinstein]

I'm very glad to see this -- please consider also allowing the named form as a input only alternative, ideally on by default. That way all maps using mapbox-gl will automatically be able to accept pasted-in URLs from OSM without barfing.

[andrewharvey]

was closed by #8603