move gotd fork into repo. (#111)

- update to latest telegram layer
- remove some references to fields in tg.Entities that don't exist in
the schema
- originally added here:
https://github.com/beeper/td/commit/820929062a2ba0104397bc01235ab58a9cff780e
  - referenced here
-
https://github.com/mautrix/telegramgo/commit/124f0967ed195b5a380c9bd02e170ada9710dde3
-
https://github.com/mautrix/telegramgo/commit/4205047aab2e0639217148b5d125bfaab668bd8e

pkg/gotd/wsutil/conn.go

@@ -0,0 +1,13 @@
+package wsutil
+
+import (
+	"context"
+	"net"
+
+	"github.com/coder/websocket"
+)
+
+// NetConn creates opaque wrapper net.Conn for websocket.Conn.
+func NetConn(c *websocket.Conn) net.Conn {
+	return websocket.NetConn(context.Background(), c, websocket.MessageBinary)
+}