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/cmd/gotdecho/main.go

@@ -0,0 +1,49 @@
+// Binary gotdecho provides example of Telegram echo bot.
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+
+	"go.mau.fi/mautrix-telegram/pkg/gotd/telegram"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/telegram/message"
+	"go.mau.fi/mautrix-telegram/pkg/gotd/tg"
+)
+
+func run(ctx context.Context) error {
+	logger, _ := zap.NewDevelopment(zap.IncreaseLevel(zapcore.DebugLevel))
+	defer func() { _ = logger.Sync() }()
+
+	dispatcher := tg.NewUpdateDispatcher()
+	return telegram.BotFromEnvironment(ctx, telegram.Options{
+		Logger:        logger,
+		UpdateHandler: dispatcher,
+	}, func(ctx context.Context, client *telegram.Client) error {
+		sender := message.NewSender(tg.NewClient(client))
+		dispatcher.OnNewMessage(func(ctx context.Context, entities tg.Entities, u *tg.UpdateNewMessage) error {
+			m, ok := u.Message.(*tg.Message)
+			if !ok || m.Out {
+				return nil
+			}
+
+			_, err := sender.Reply(entities, u).Text(ctx, m.Message)
+			return err
+		})
+		return nil
+	}, telegram.RunUntilCanceled)
+}
+
+func main() {
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
+	defer cancel()
+
+	if err := run(ctx); err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "%+v\n", err)
+		os.Exit(2)
+	}
+}