Requested Changes for Editor Knossos Implementation (#129)

* placeholder

* max length & placeholder

* Accept editor comment conflict

* integrate requested features

* null check for ref

* Change prompt for image upload

* change filter for proper input blocking

* Add spoiler button

* change url of helper link

* shallow resource link style

* resource link inherit site style

* detach preview styling from markdown-body style

* remove sizing dependance on global styles

* Bump 0.6.5

lib/assets/styles/classes.scss

@@ -883,7 +883,7 @@ a,
 
   a {
     cursor: pointer;
-    color: var(--color-blue);
+    color: var(--color-link);
 
     &:focus-visible,
     &:hover {