Dashboard: extend dashnav to add custom content (#23433)

public/app/features/dashboard/components/DashNav/DashNav.tsx

 // Libaries
-import React, { PureComponent } from 'react';
+import React, { PureComponent, FC } from 'react';
 import { connect } from 'react-redux';
 import { css } from 'emotion';
 import { e2e } from '@grafana/e2e';
@@ -29,6 +29,12 @@ export interface OwnProps {
   onAddPanel: () => void;
 }
 
+const customNavbarContent: Array<FC<Partial<OwnProps>>> = [];
+
+export function addNavbarContent(content: FC<Partial<OwnProps>>) {
+  customNavbarContent.push(content);
+}
+
 export interface StateProps {
   location: any;
 }
@@ -173,6 +179,10 @@ class DashNav extends PureComponent<Props> {
           </div>
         )}
 
+        {customNavbarContent.map((Component, index) => (
+          <Component {...this.props} key={`navbar-custom-content-${index}`} />
+        ))}
+
         <div className="navbar-buttons navbar-buttons--actions">
           {canSave && (
             <DashNavButton