Fix description

manifest.json

@@ -2,7 +2,7 @@
     "manifest_version": 2,
     "name"            : "Markdown Viewer",
     "version"         : "1.4",
-    "description"     : "Markdown viewer",
+    "description"     : "Markdown Viewer",
 
     "page_action": {
         "default_icon": {