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/td.go

@@ -0,0 +1,11 @@
+// Package td implements MTProto encoding and decoding.
+package td
+
+//go:generate go run go.mau.fi/mautrix-telegram/pkg/gotd/cmd/gotdgen --doc "https://core.telegram.org/" --clean --server --handlers --mapping --slices --package tg --target tg --schema _schema/telegram.tl
+//go:generate go run go.mau.fi/mautrix-telegram/pkg/gotd/cmd/gotdgen --doc "https://core.telegram.org/" --clean --package e2e --target tg/e2e --schema _schema/encrypted.tl
+
+//go:generate go run go.mau.fi/mautrix-telegram/pkg/gotd/cmd/gotdgen --clean --package tdapi --tdlib-json --target tdapi --schema _schema/tdapi.tl
+
+//go:generate go run go.mau.fi/mautrix-telegram/pkg/gotd/cmd/gotdgen --clean --client=false --package tgtrace --target tgtrace --schema _schema/trace.tl
+
+//go:generate go run go.mau.fi/mautrix-telegram/pkg/gotd/cmd/gotdgen --clean --package mt --target mt --client=false --schema _schema/mt.tl