Add TagEvent.

src/tag.rs

@@ -1 +1,30 @@
 //! Types for the *m.tag* event.
+
+use std::collections::HashMap;
+
+use core::{Event, EventType};
+
+/// Informs the client of tags on a room.
+pub struct TagEvent<'a> {
+    /// The payload.
+    content: TagEventContent<'a>,
+}
+
+impl<'a> Event<'a, TagEventContent<'a>> for TagEvent<'a> {
+    fn content(&'a self) -> &'a TagEventContent<'a> {
+        &self.content
+    }
+
+    fn event_type(&self) -> EventType {
+        EventType::Tag
+    }
+}
+
+/// The payload of a `TagEvent`.
+pub struct TagEventContent<'a> {
+    /// The list of user IDs typing in this room, if any.
+    tags: &'a Tags<'a>,
+}
+
+/// A map of tag names to values.
+pub type Tags<'a> = HashMap<&'a str, &'a str>;