make rollbar props optional & export extension point

plugins/rollbar/src/components/EntityPageRollbar/EntityPageRollbar.tsx

@@ -21,7 +21,7 @@ import { RollbarProject } from '../RollbarProject/RollbarProject';
 
 type Props = {
   /** @deprecated The entity is now grabbed from context instead */
-  entity: Entity;
+  entity?: Entity;
 };
 
 export const EntityPageRollbar = (_props: Props) => {

plugins/rollbar/src/components/Router.tsx

@@ -28,7 +28,7 @@ export const isPluginApplicableToEntity = (entity: Entity) =>
 
 type Props = {
   /** @deprecated The entity is now grabbed from context instead */
-  entity: Entity;
+  entity?: Entity;
 };
 
 export const Router = (_props: Props) => {

plugins/rollbar/src/index.ts

@@ -22,4 +22,8 @@ export {
   Router,
 } from './components/Router';
 export { ROLLBAR_ANNOTATION } from './constants';
-export { rollbarPlugin as plugin, rollbarPlugin } from './plugin';
+export {
+  EntityRollbarContent,
+  rollbarPlugin as plugin,
+  rollbarPlugin,
+} from './plugin';