Line-wrap first paragraph, update link and parameters

Co-authored-by: Kévin Commaille <76261501+zecakeh@users.noreply.github.com>

data/event-schemas/examples/m.room.topic.yaml

@@ -6,11 +6,11 @@
     "m.topic": {
       "m.text": [ {
         "mimetype": "text/html",
-        "body": "An <em>html</em> topic"
+        "body": "An <em>interesting</em> room topic"
       }, {
-        "body": "A plain text topic"
+        "body": "An interesting room topic"
       }]
     },
-    "topic": "A plain text topic"
+    "topic": "An interesting room topic"
   }
 }

data/event-schemas/schema/m.room.topic.yaml

@@ -2,7 +2,12 @@
 allOf:
   - $ref: core-event-schema/state_event.yaml
 description: |-
-  A topic is a short message detailing what is currently being discussed in the room.  It can also be used as a way to display extra information about the room, which may not be suitable for the room name. The room topic can also be set when creating a room using `/createRoom` with the `topic` key.
+  A topic is a short message detailing what is currently being discussed
+  in the room.  It can also be used as a way to display extra information
+  about the room, which may not be suitable for the room name. The room
+  topic can be set when creating a room using
+  [`/createRoom`](client-server-api/#post_matrixclientv3createroom), either
+  with the `topic` key or by specifying a full event in `initial_state`.
   
   In order to prevent formatting abuse in room topics, clients SHOULD
   limit the length of topics during both entry and display, for instance,