Add logo/favicon, closes #1849

.gitignore

@@ -7,3 +7,5 @@ composer.lock
 .hg
 .phpunit.result.cache
 .phpunit.cache
+favicon.ico
+logo.jpg

README.md

@@ -1,3 +1,5 @@
+![Monolog](logo.jpg)
+
 # Monolog - Logging for PHP [![Continuous Integration](https://github.com/Seldaek/monolog/workflows/Continuous%20Integration/badge.svg?branch=main)](https://github.com/Seldaek/monolog/actions)
 
 [![Total Downloads](https://img.shields.io/packagist/dt/monolog/monolog.svg)](https://packagist.org/packages/monolog/monolog)