OSM OpenMapTiles style (#1420)

* OpenMapTiles style

* Rename style snippets from layer_name.json to defaultstyle.json

* Add README to icons dir.

* Add README to icons dir.

* Rename snippets to style.json

* Fix spritezero - move icons to svg subdir

* Move icons from style/icons/svg directly to style/icons

Co-authored-by: Tomas Pohanka <TomPohys@gmail.com>

style/icons/square_train.svg

@@ -0,0 +1,10 @@
+<svg width="6" height="6" viewBox="0 0 6 6" fill="none" xmlns="http://www.w3.org/2000/svg">
+<g clip-path="url(#clip0)">
+<path d="M0 0V6H6V0H0Z" fill="#8461C4"/>
+</g>
+<defs>
+<clipPath id="clip0">
+<rect width="6" height="6" fill="white"/>
+</clipPath>
+</defs>
+</svg>