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/thumbnail/svg.go

@@ -0,0 +1,45 @@
+package thumbnail
+
+import (
+	"strconv"
+)
+
+// DecodePath decodes vector thumbnail from thumbnail bytes (e.g. tg.PhotoPathSize with type "j").
+//
+// See DecodePathTo.
+func DecodePath(data []byte) []byte {
+	return DecodePathTo(data, nil)
+}
+
+// DecodePathTo decodes vector thumbnail to given slice.
+//
+// Returned path will contain the actual SVG path that can
+// be directly inserted in the d attribute of an svg <path> element:
+//
+//	<?xml version="1.0" encoding="utf-8"?>
+//	<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"
+//	   viewBox="0 0 512 512" xml:space="preserve">
+//	<path d="{$path}"/>
+//	</svg>
+//
+// See https://core.telegram.org/api/files#vector-thumbnails.
+func DecodePathTo(data, to []byte) []byte {
+	const (
+		lookup = "AACAAAAHAAALMAAAQASTAVAAAZaacaaaahaaalmaaaqastava.az0123456789-,"
+	)
+	to = append(to, 'M')
+	for _, num := range data {
+		if num >= 128+64 {
+			to = append(to, lookup[int(num-128-64)])
+		} else {
+			if num >= 128 {
+				to = append(to, ',')
+			} else if num >= 64 {
+				to = append(to, '-')
+			}
+			to = strconv.AppendInt(to, int64(num&63), 10)
+		}
+	}
+	to = append(to, 'z')
+	return to
+}