Implement MSC3869: Read event relations with the Widget API (#9210)

* Add an action to read relations according to MSC3869

Signed-off-by: Dominik Henneke <dominik.henneke@nordeck.net>

* Apply review comments

Signed-off-by: Dominik Henneke <dominik.henneke@nordeck.net>

* Fix test

Signed-off-by: Dominik Henneke <dominik.henneke@nordeck.net>

* Update matrix-widget-api to 1.1.1

Signed-off-by: Dominik Henneke <dominik.henneke@nordeck.net>

Signed-off-by: Dominik Henneke <dominik.henneke@nordeck.net>

package.json

@@ -94,7 +94,7 @@
     "matrix-encrypt-attachment": "^1.0.3",
     "matrix-events-sdk": "^0.0.1-beta.7",
     "matrix-js-sdk": "github:matrix-org/matrix-js-sdk#develop",
-    "matrix-widget-api": "^1.0.0",
+    "matrix-widget-api": "^1.1.1",
     "minimist": "^1.2.5",
     "opus-recorder": "^8.0.3",
     "pako": "^2.0.3",