Update doc

Author: jcs090218

README.md

@@ -1 +1,18 @@
-# fextern
+[![License: GPL v3](https://img.shields.io/badge/License-GPL%20v3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
+[![JCS-ELPA](https://raw.githubusercontent.com/jcs-emacs/jcs-elpa/master/badges/v/fextern.svg)](https://jcs-emacs.github.io/jcs-elpa/#/fextern)
+
+# fextern
+> Record file external states
+
+[![CI](https://github.com/emacs-vs/fextern/actions/workflows/test.yml/badge.svg)](https://github.com/emacs-vs/fextern/actions/workflows/test.yml)
+
+## Contribute
+
+[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](http://makeapullrequest.com)
+[![Elisp styleguide](https://img.shields.io/badge/elisp-style%20guide-purple)](https://github.com/bbatsov/emacs-lisp-style-guide)
+[![Donate on paypal](https://img.shields.io/badge/paypal-donate-1?logo=paypal&color=blue)](https://www.paypal.me/jcs090218)
+
+If you would like to contribute to this project, you may either
+clone and make pull requests to this repository. Or you can
+clone the project and establish your own branch of this tool.
+Any methods are welcome!