Extension support page (#1112)

Signed-off-by: Roman <ixrock@gmail.com>
Co-authored-by: Jim Ehrismann <40840436+jim-docker@users.noreply.github.com>

src/extensions/registries/base-registry.ts

@@ -0,0 +1,17 @@
+// Base class for extensions-api registries
+import { observable } from "mobx";
+
+export class BaseRegistry<T = any> {
+  protected items = observable<T>([], { deep: false });
+
+  getItems(): T[] {
+    return this.items.toJS();
+  }
+
+  add(item: T) {
+    this.items.push(item);
+    return () => {
+      this.items.remove(item); // works because of {deep: false};
+    }
+  }
+}