Initial migration to typescript (#845)

This migrates some utilities classes from javascript to typescript.
Nothing special about the migration, mainly added types and made sure
the code adheres to the strict mode.

I have picked some small files so git doesn't think they are the same
since they are "very different".
I hope that in later PRs, when migrating lager files this won't be an
issues.

src/libs/zoomcontrol.ts

@@ -0,0 +1,37 @@
+import {Map} from 'maplibre-gl';
+
+export default class ZoomControl {
+  _map: Map| undefined = undefined;
+  _container: HTMLDivElement | undefined = undefined;
+  _textEl: HTMLSpanElement | null = null;
+
+  onAdd(map: Map) {
+    this._map = map;
+    this._container = document.createElement('div');
+    this._container.className = 'maplibregl-ctrl maplibregl-ctrl-group maplibregl-ctrl-zoom';
+    this._container.setAttribute("data-wd-key", "maplibre:ctrl-zoom");
+    this._container.innerHTML = `
+      Zoom: <span></span>
+    `;
+    this._textEl = this._container.querySelector("span");
+    
+    this.addEventListeners();
+    
+    return this._container;
+  }
+  
+  updateZoomLevel() {
+    this._textEl!.innerHTML = this._map!.getZoom().toFixed(2);
+  }
+  
+  addEventListeners (){
+    this._map!.on('render', () => this.updateZoomLevel());
+    this._map!.on('zoomIn', () => this.updateZoomLevel());
+    this._map!.on('zoomOut', () => this.updateZoomLevel());
+  }
+
+  onRemove() {
+    this._container!.parentNode!.removeChild(this._container!);
+    this._map = undefined;
+  }
+}