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/bin/errors.go

@@ -0,0 +1,27 @@
+package bin
+
+import "fmt"
+
+// InvalidLengthError is returned when decoder reads invalid length.
+type InvalidLengthError struct {
+	Length int
+	Where  string
+}
+
+func (i *InvalidLengthError) Error() string {
+	return fmt.Sprintf("invalid %s length: %d", i.Where, i.Length)
+}
+
+// UnexpectedIDErr means that unknown or unexpected type id was decoded.
+type UnexpectedIDErr struct {
+	ID uint32
+}
+
+func (e *UnexpectedIDErr) Error() string {
+	return fmt.Sprintf("unexpected id %#x", e.ID)
+}
+
+// NewUnexpectedID return new UnexpectedIDErr.
+func NewUnexpectedID(id uint32) error {
+	return &UnexpectedIDErr{ID: id}
+}