Allow Data URLs in offlineRegionDefinitions styleURL

[mariusvn]

Is your feature request related to a problem? Please describe. The offline region definition require an URL to define the style of the downloaded data. This makes the download of custom style generated on the fly impossible.

Describe the solution you'd like Would be nice to allow raw json or data URL that contains a style definition.

Describe alternatives you've considered As i said before, I tried with the data URLs in the style URL but it doesn't seems like the URL parser parse it.

Additional context MapLibre gives me this message followed by the content of the styleURL: [HTTP] Unable to parse resourceUrl