(docs) add message bg & colors

Author: antoine92190

README.md

@@ -137,7 +137,11 @@ colors="{
   menuBg: '#fff',
   menuBgHover: '#f6f6f6',
   messagesBg: '#f8f9fa',
-  textColorDark: '#0a0a0a',
+  messageBg: '#fff',
+  messageMeBg: '#ccf2cf',
+  messageUsernameColor: '#9ca6af',
+  messageTimestampColor: '#828c94',
+  messageTextColor: '#0a0a0a',
   textColor: '#0a0a0a',
   inputBg: '#fff',
   spinnerColor: '#333',