Allow for webp tiles sources

[jo-chemla]

Hi there, following #60, there is a bug with webp tile sources that cannot be validated by NextGIS QMS? The source loads correctly on the leaflet map canvas, but cannot be made public with error Service is failing validation and can't be made public. Edit it to fix errors or let us know. + errors comes with text service response is not image.

https://qms.nextgis.com/geoservices/6088/

[jo-chemla]

Hi there, wondering if you had time to allow webp tiles in NextGIS QMS - I still cannot publish the Mapbox Service which cannot be validated, although it is shown on the leaflet viewer, simply because tiles are webp. If there is anything I can do to help push webp tiles TMS, let me know! At the moment, the mapbox satellite source still fails validation https://qms.nextgis.com/geoservices/6088/ (message cross-posted from a closed PR since this issue is still open)