fix(mdviewer): disable spellcheck and autocorrect in edit mode

Set spellcheck=false, autocorrect=off, autocapitalize=off on
viewer-content when entering edit mode to prevent browser squiggly
underlines on contenteditable text.

Author: abose

src-mdviewer/src/components/editor.js

@@ -1553,6 +1553,9 @@ export function initEditor() {
 
 function enterEditMode(content) {
     content.setAttribute("contenteditable", "true");
+    content.setAttribute("spellcheck", "false");
+    content.setAttribute("autocorrect", "off");
+    content.setAttribute("autocapitalize", "off");
     content.classList.add("editing");
 
     document.execCommand("defaultParagraphSeparator", false, "p");