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/html/stack.go

@@ -0,0 +1,35 @@
+package html
+
+import "go.mau.fi/mautrix-telegram/pkg/gotd/telegram/message/entity"
+
+type stackElem struct {
+	token  entity.Token
+	tag    string
+	attr   string
+	format entity.Formatter
+}
+
+type stack []stackElem
+
+func (s *stack) push(e stackElem) {
+	*s = append(*s, e)
+}
+
+func (s *stack) last() (stackElem, bool) {
+	l := len(*s)
+	if l == 0 {
+		return stackElem{}, false
+	}
+
+	elem := (*s)[l-1]
+	return elem, true
+}
+
+func (s *stack) pop() (stackElem, bool) {
+	e, ok := s.last()
+	if !ok {
+		return stackElem{}, false
+	}
+	*s = (*s)[:len(*s)-1]
+	return e, true
+}