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/telegram/message/gif.go

@@ -0,0 +1,26 @@
+package message
+
+import (
+	"context"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+// GIF add attributes to create GIF attachment.
+func (u *UploadedDocumentBuilder) GIF() *UploadedDocumentBuilder {
+	return u.Attributes(&tg.DocumentAttributeAnimated{}).
+		MIME(DefaultGifMIME)
+}
+
+// GIF adds gif attachment.
+func GIF(file tg.InputFileClass, caption ...StyledTextOption) *UploadedDocumentBuilder {
+	return UploadedDocument(file, caption...).GIF()
+}
+
+// GIF sends gif.
+func (b *Builder) GIF(
+	ctx context.Context,
+	file tg.InputFileClass, caption ...StyledTextOption,
+) (tg.UpdatesClass, error) {
+	return b.Media(ctx, GIF(file, caption...))
+}