README.md: Update TDLib badge to 1.8.20

README.md

@@ -1,4 +1,4 @@
-[![CI test](https://github.com/zevlg/telega.el/workflows/CI/badge.svg)](https://github.com/zevlg/telega.el/actions) [![DOCKER image build](https://github.com/zevlg/telega.el/workflows/DOCKER/badge.svg)](https://github.com/zevlg/telega.el/actions) [![Telegram chat](https://img.shields.io/badge/chat-%40emacs__telega-%2335ADE1?logo=telegram)](https://t.me/emacs_telega) [![TDLib](https://img.shields.io/badge/TDLib-v1.8.15-%2335ADE1)](https://github.com/tdlib/td) [![MELPA](https://melpa.org/packages/telega-badge.svg)](https://melpa.org/#/telega) [![MELPA Stable](http://stable.melpa.org/packages/telega-badge.svg)](http://stable.melpa.org/#/telega) [![GNU Guix](https://img.shields.io/badge/GNU%20Guix-0.7.1-blue)](https://guix.gnu.org/packages/emacs-telega-0.7.1-1.1d28dc2/) [![Open Collective](https://img.shields.io/opencollective/backers/telega?logo=opencollective)](https://opencollective.com/telega)
+[![CI test](https://github.com/zevlg/telega.el/workflows/CI/badge.svg)](https://github.com/zevlg/telega.el/actions) [![DOCKER image build](https://github.com/zevlg/telega.el/workflows/DOCKER/badge.svg)](https://github.com/zevlg/telega.el/actions) [![Telegram chat](https://img.shields.io/badge/chat-%40emacs__telega-%2335ADE1?logo=telegram)](https://t.me/emacs_telega) [![TDLib](https://img.shields.io/badge/TDLib-v1.8.20-%2335ADE1)](https://github.com/tdlib/td) [![MELPA](https://melpa.org/packages/telega-badge.svg)](https://melpa.org/#/telega) [![MELPA Stable](http://stable.melpa.org/packages/telega-badge.svg)](http://stable.melpa.org/#/telega) [![GNU Guix](https://img.shields.io/badge/GNU%20Guix-0.7.1-blue)](https://guix.gnu.org/packages/emacs-telega-0.7.1-1.1d28dc2/) [![Open Collective](https://img.shields.io/opencollective/backers/telega?logo=opencollective)](https://opencollective.com/telega)
 
 [![Backers](https://opencollective.com/telega/backers.svg?avatarHeight=32&width=600)](https://opencollective.com/telega)