Add Liberapay icon (#2192)

https://liberapay.com/FreshRSS
https://github.com/FreshRSS/FreshRSS/issues/1694

README.fr.md

@@ -1,4 +1,5 @@
-[![Build Status](https://travis-ci.org/FreshRSS/FreshRSS.svg)](https://travis-ci.org/FreshRSS/FreshRSS)
+[![Statut de la compilation](https://travis-ci.org/FreshRSS/FreshRSS.svg)](https://travis-ci.org/FreshRSS/FreshRSS)
+[![Dons Liberapay](https://img.shields.io/liberapay/receives/FreshRSS.svg?logo=liberapay)](https://liberapay.com/FreshRSS/donate)
 
 * Lire ce document sur [github.com/FreshRSS/FreshRSS/](https://github.com/FreshRSS/FreshRSS/blob/master/README.md) pour avoir les images et liens corrects.
 * [English version](README.md)

README.md

@@ -1,4 +1,5 @@
 [![Build Status][travis-badge]][travis-link]
+[![Liberapay donations](https://img.shields.io/liberapay/receives/FreshRSS.svg?logo=liberapay)](https://liberapay.com/FreshRSS/donate)
 
 * Read this document on [github.com/FreshRSS/FreshRSS/](https://github.com/FreshRSS/FreshRSS/blob/master/README.md) to get the correct links and pictures.
 * [Version française](README.fr.md)