Add document insights panel (#4418)

* Add document context to allow accessing editor in header, modals, and elsewhere

* lint

* framework

* Hacking together fast

* Insights

* Spacing tweak, docs

app/routes/authenticated.tsx

@@ -106,6 +106,7 @@ function AuthenticatedRoutes() {
               path={`/doc/${slug}/history/:revisionId?`}
               component={Document}
             />
+            <Route exact path={`/doc/${slug}/insights`} component={Document} />
             <Route exact path={`/doc/${slug}/edit`} component={Document} />
             <Route path={`/doc/${slug}`} component={Document} />
             <Route exact path="/search" component={Search} />