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/session/tdesktop/md5.go

@@ -0,0 +1,20 @@
+package tdesktop
+
+import (
+	"crypto/md5" // #nosec G501
+	"encoding/hex"
+	"strings"
+)
+
+func tdesktopMD5(s string) string {
+	hash := md5.Sum([]byte(s)) // #nosec G401
+	for i := range hash {
+		hash[i] = hash[i]<<4 | hash[i]>>4
+	}
+	hexed := hex.EncodeToString(hash[:])
+	return strings.ToUpper(hexed)
+}
+
+func fileKey(s string) string {
+	return tdesktopMD5(s)[:16]
+}