Migrate all the non react components code to typescript (#847)

This completes the migration to typescript of all the non react
components code.
The only changes introduced besides types are the type checks using
`"something" in object` which narrows down types in typescript.

src/libs/source.ts

@@ -0,0 +1,27 @@
+import type {StyleSpecification, SourceSpecification} from "@maplibre/maplibre-gl-style-spec";
+
+export function deleteSource(mapStyle: StyleSpecification, sourceId: string) {
+  const remainingSources = { ...mapStyle.sources}
+  delete remainingSources[sourceId]
+  return {
+    ...mapStyle,
+    sources: remainingSources
+  }
+}
+
+
+export function addSource(mapStyle: StyleSpecification, sourceId: string, source: SourceSpecification) {
+  return changeSource(mapStyle, sourceId, source)
+}
+
+export function changeSource(mapStyle: StyleSpecification, sourceId: string, source: SourceSpecification) {
+  const changedSources = {
+    ...mapStyle.sources,
+    [sourceId]: source
+  }
+  return {
+    ...mapStyle,
+    sources: changedSources
+  }
+}
+