Add TileServer GL

Ref #1284, in addition to OpenMapTiles TileServer PHP

The licenses listed in https://github.com/klokantech/tileserver-gl/blob/master/LICENSE.md are:

BSD-2-Clause, Apache-2.0, [Boost](https://en.wikipedia.org/wiki/Boost_(C%2B%2B_libraries)#License), MIT, BSD-3-Clause; [libpng](https://en.wikipedia.org/wiki/Libpng_License), ISC, [OpenSSL](https://www.openssl.org/source/license.html), [zlib](https://en.wikipedia.org/wiki/zlib_License), sqlite/Public Domain

README.md

@@ -791,6 +791,7 @@ _Command-line file upload_
 - [Openstreetmap](http://www.openstreetmap.org/) - OpenStreetMap is a map of the world, created by people like you and free to use under an open license. ([Source Code](https://github.com/openstreetmap/openstreetmap-website)) `GPL-2.0` `Ruby`
 - [Orion](https://github.com/LINKIWI/orion-web) - Powerful OwnTracks API-compliant location data visualization frontend for the web. ([Demo](https://linkiwi.github.io/orion-web/)) `MIT` `Python/Nodejs`
 - [OwnTracks Recorder](https://github.com/owntracks/recorder) `⚠` - Store and access data published by [OwnTracks](http://owntracks.org/) location tracking apps. `GPL-2.0` `C`/`Lua`
+- [TileServer GL](http://tileserver.readthedocs.io/) - Vector and raster maps with GL styles. Server side rendering by Mapbox GL Native. Map tile server for Mapbox GL JS, Android, iOS, Leaflet, OpenLayers, GIS via WMTS, etc. ([Source Code](https://github.com/klokantech/tileserver-gl)) `Multiple` `Nodejs`
 - [Traccar](https://www.traccar.org/) - Java application to track GPS positions. Supports loads of tracking devices and protocols, has an Android and iOS App. Has a web interface to view your trips. ([Demo](http://demo.traccar.org/), [Source Code](https://github.com/tananaev?tab=repositories)) `Apache-2.0` `Java`
 - [uMap](https://umap.openstreetmap.fr/en/) - Create maps with OpenStreetMap layers in a minute and embed them in your site. ([Source Code](https://github.com/umap-project/umap)) `WTFPL` `Python`