perf: Reduce initial bundle size / async bundle loading (#1456)

* feat: Move to React.lazy

* perf: Remove duplicate babel/runtime

* fix: Run yarn-deduplicate

* Further attempts to remove rich-markdown-editor from initial chunk

* perf: Lazy loading of authenticated routes

* perf: Move color picker to async loading
fix: Display placeholder when loading rich editor

* fix: Cache bust on auto reload

shared/utils/parseDocumentSlug.js

@@ -0,0 +1,12 @@
+// @flow
+
+export function parseDocumentSlugFromUrl(url: string) {
+  let parsed;
+  try {
+    parsed = new URL(url);
+  } catch (err) {
+    return;
+  }
+
+  return parsed.pathname.replace(/^\/doc\//, "");
+}