fix: run linkify checks on entire parent tree

A lot of web editors create elaborate DOM trees and it is not enough to
check if parent is safe for linkification.

This change walks back over entire parent tree to ensure none of parents
has a no-go flag for linkification (eg. HTMLElement.contentEditable property)

add-on/src/contentScripts/linkifyDOM.js

@@ -139,16 +139,28 @@ const PQueue = require('p-queue')
     return window.ipfsCompanionLinkifyValidationCache.get(path)
   }
 
-  async function linkifyTextNode (node) {
-    const parent = node.parentNode
+  function isParentTreeSafe (node) {
+    let parent = node.parentNode
     // Skip if no longer in visible DOM
-    if (!parent) return
-    // Skip already linkified nodes
-    if (parent.className && parent.className.match(/\blinkifiedIpfsAddress\b/)) return
-    // Skip styled <pre> -- often highlighted by script.
-    if (parent.tagName === 'PRE' && parent.className) return
-    // Skip forms, textareas
-    if (parent.isContentEditable) return
+    if (!parent) return false
+    // Walk back over parent tree and check each of them
+    while (parent) {
+      // Skip forms, textareas
+      if (parent.isContentEditable) return false
+      // Skip already linkified nodes
+      if (parent.className && parent.className.match(/\blinkifiedIpfsAddress\b/)) return false
+      // Skip styled <pre> -- often highlighted by scripts
+      if (parent.tagName === 'PRE' && parent.className) return false
+      // Skip if no longer in visible DOM
+      if (!(parent instanceof HTMLDocument) && !parent.parentNode) return false
+      parent = parent.parentNode
+    }
+    return true
+  }
+
+  async function linkifyTextNode (node) {
+    // Skip if node belongs to a parent from unsafe tree
+    if (!isParentTreeSafe(node)) return
 
     let link
     let match