add & deprecate old markdownSummary export

src/core.ts

@@ -364,3 +364,8 @@ export async function getIDToken(aud?: string): Promise<string> {
  * Summary exports
  */
 export {summary} from './summary'
+
+/**
+ * @deprecated use core.summary
+ */
+export {markdownSummary} from './summary'

src/summary.ts

@@ -354,5 +354,10 @@ class Summary {
   }
 }
 
-// singleton export
-export const summary = new Summary()
+const _summary = new Summary()
+
+/**
+ * @deprecated use `core.summary`
+ */
+export const markdownSummary = _summary
+export const summary = _summary