Highlight *.pac files as JavaScript

closes #1515

src/syntax_mapping.rs

@@ -42,6 +42,9 @@ impl<'a> SyntaxMapping<'a> {
                 MappingTarget::MapTo("Bourne Again Shell (bash)"),
             )
             .unwrap();
+        mapping
+            .insert("*.pac", MappingTarget::MapTo("JavaScript (Babel)"))
+            .unwrap();
 
         // See #1008
         mapping