Merge ba06828931 into c578129bed

* Spec for MSC4313: Require HTML <ol> start Attribute support

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

* Add changelog

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

* Apply suggestion

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

---------

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

changelogs/client_server/newsfragments/2299.feature

@@ -0,0 +1 @@
+Clients supporting the `ol` HTML element must also support the `start` attribute, as per [MSC4313](https://github.com/matrix-org/matrix-spec-proposals/pull/4313).

changelogs/client_server/newsfragments/2304.clarification

@@ -0,0 +1 @@
+Clarify the requiredness of `event_id` in `predecessor`.

content/client-server-api/modules/instant_messaging.md

@@ -84,6 +84,10 @@ Additionally, web clients should ensure that *all* `a` tags get a
 `rel="noopener"` to prevent the target page from referencing the
 client's tab/window.
 
+{{% added-in v="1.18" %}} Clients that support rendering numbered lists via the
+`ol` tag MUST also support the `start` attribute in order to prevent loss of
+meaning of a message due to the numbering of list items.
+
 Tags must not be nested more than 100 levels deep. Clients should only
 support the subset of tags they can render, falling back to other
 representations of the tags where possible. For example, a client may

content/client-server-api/modules/room_upgrades.md

@@ -43,8 +43,8 @@ They must be explicitly set during the `/upgrade` call.
 {{% /boxes/note %}}
 
 {{% boxes/note %}}
-{{% added-in v="1.16" %}} When upgrading to room version 12 or later, the `predecessor` field MAY NOT contain
-an `event_id`.
+{{% added-in v="1.16" %}} When upgrading to room version 12 or later, the `event_id` property inside
+`predecessor` MAY be omitted.
 {{% /boxes/note %}}
 
 3.  Replicates transferable state events to the new room. The exact