Support delayed events (MSC4140) for call widget (#12714)

The Widget API spec for delayed events is defined by MSC4157.

Also support "parent" delayed events, which were in a previous version
of MSC4140 and may be reintroduced or be part of a new MSC later.

package.json

@@ -119,7 +119,7 @@
         "matrix-encrypt-attachment": "^1.0.3",
         "matrix-events-sdk": "0.0.1",
         "matrix-js-sdk": "github:matrix-org/matrix-js-sdk#develop",
-        "matrix-widget-api": "^1.5.0",
+        "matrix-widget-api": "^1.8.2",
         "memoize-one": "^6.0.0",
         "minimist": "^1.2.5",
         "oidc-client-ts": "^3.0.1",