Added basic HTML tag syntax highlight styling

src/css/simplemde.css

@@ -268,6 +268,18 @@
 	padding: 5px;
 }
  
+.CodeMirror .CodeMirror-code .cm-tag {
+	color: #63a35c;
+}
+
+.CodeMirror .CodeMirror-code .cm-attribute {
+	color: #795da3;
+}
+
+.CodeMirror .CodeMirror-code .cm-string {
+	color: #183691;
+}
+
 .CodeMirror .CodeMirror-selected {
 	background: #d9d9d9;
 }