add proposal xxxx-copy-room-type-on-upgrade.md

Signed-off-by: Aminda Suomalainen <suomalainen+git@mikaela.info>

proposals/xxxx-copy-room-type-on-upgrade.md

@@ -0,0 +1,36 @@
+# MSCXXXX: Copy room type on upgrade.
+
+There can never be enough templates in the world, and MSCs shouldn't be any different. The level
+of detail expected of proposals can be unclear - this is what this example proposal (which doubles
+as a template itself) aims to resolve.
+
+Unless the room upgrade API specifies that room type must be copied over, clients cannot rely on
+rooms staying the same type leading to trouble.
+
+
+## Proposal
+
+This MSC proposes that the room upgade API MUST copy the room type over to the new room. Otherwise
+clients cannot trust that to happen and Spaces or MSC3588 Story rooms may incorrectly become normal
+rooms breaking user-experience.
+
+
+## Potential issues
+
+Non-applicable.
+
+## Alternatives
+
+Non-applicable.
+
+## Security considerations
+
+Non-applicable.
+
+## Unstable prefix
+
+Non-applicable.
+
+## Dependencies
+
+Non-applicable.