Add missing Arabic translations for 'author', 'see_also' and 'posts' (#474)

i18n/ar.toml

@@ -21,3 +21,12 @@ other = "بإمكانك العودة إلى <a href=\"{{ . }}\">homepage</a>."
 
 [powered_by]
 other = "بواسطة"
+
+[author]
+other = "الكاتب"
+
+[see_also]
+other = "انظر أيضاً"
+
+[posts]
+other = "المنشورات"