No More Collab. Fixes #449

* Fully removes real-time collaboration
* URL scheme rewrite

plug-api/lib/page.ts

@@ -0,0 +1,4 @@
+export function isValidPageName(name: string): boolean {
+  // Page can not be empty and not end with a file extension (e.g. "bla.md")
+  return name !== "" && !/\.[a-zA-Z]+$/.test(name);
+}