`regex.containsMatchIn()` for `.*@room.*` can take significantly longer
than checking for `@room` (some real-world events I was getting took
around 15 seconds with this, significantly slowing down the sync
parsing).
Checking `containsMatchIn()` does not lead to different results when
having leading and trailing stars however, it will match in the same
cases as when these are omitted.
For testing purposes, I sent myself some Lorem Ipsum with 5000 words
(not containing any @room).
Without this change, the regex evaluation takes about 16 seconds.
With this change, the regex evaluation now takes significantly less then
a second.
