improve(sanitizer): add more allowed attributes (#4194)

* Add a couple of items to the sanitizeOptions

*  Strings must use doublequote  quotes

src/core/components/providers/markdown.jsx

@@ -29,10 +29,12 @@ Markdown.propTypes = {
 export default Markdown
 
 const sanitizeOptions = {
-    allowedTags: sanitize.defaults.allowedTags.concat([ "h1", "h2", "img" ]),
+    allowedTags: sanitize.defaults.allowedTags.concat([ "h1", "h2", "img", "span" ]),
     allowedAttributes: {
         ...sanitize.defaults.allowedAttributes,
-        "img": sanitize.defaults.allowedAttributes.img.concat(["title"])
+        "img": sanitize.defaults.allowedAttributes.img.concat(["title"]),
+        "td": [ "colspan" ],
+        "*": [ "class" ]
     },
     textFilter: function(text) {
         return text.replace(/"/g, "\"")