Add support for MSC4155 (#1013)

[rendered msc here](https://github.com/Johennes/matrix-spec-proposals/blob/johannes/invite-filtering/proposals/4155-invite-filtering.md). Closes #836.

Co-authored-by: nexy7574 <git@nexy7574.co.uk>
Reviewed-on: https://forgejo.ellis.link/continuwuation/continuwuity/pulls/1013
Reviewed-by: nex <nex@noreply.forgejo.ellis.link>
Co-authored-by: Ginger <ginger@gingershaped.computer>
Co-committed-by: Ginger <ginger@gingershaped.computer>

Cargo.toml

@@ -381,6 +381,7 @@ features = [
     "unstable-msc4095",
     "unstable-msc4121",
     "unstable-msc4125",
+	"unstable-msc4155",
     "unstable-msc4186",
     "unstable-msc4203", # sending to-device events to appservices
     "unstable-msc4210", # remove legacy mentions