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/fileid/encode.go

@@ -0,0 +1,20 @@
+package fileid
+
+import (
+	"encoding/base64"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/bin"
+)
+
+// EncodeFileID parses FileID to a string.
+func EncodeFileID(id FileID) (string, error) {
+	var buf bin.Buffer
+	id.encodeLatestFileID(&buf)
+	buf.Buf = append(buf.Buf, persistentIDVersion)
+	buf.Buf = rleEncode(buf.Buf)
+	return base64Encode(buf.Buf), nil
+}
+
+func base64Encode(s []byte) string {
+	return base64.RawURLEncoding.EncodeToString(s)
+}