Add keyboard shortcut navigation for grammar mistakes

- Implements Ctrl+Š/Đ keyboard shortcuts to navigate between grammar mistakes/highlights. #4

service.js

@@ -60,11 +60,11 @@ class BesService {
     this.hostElement.setAttribute('data-gramm', 'false')
     this.hostElement.setAttribute('data-gramm_editor', 'false')
     this.hostElement.setAttribute('data-enable-grammarly', 'false')
-    this.onTab = this.onTab.bind(this)
-    this.hostElement.addEventListener('keydown', this.onTab)
 
     this.onScroll = this.onScroll.bind(this)
     this.hostElement.addEventListener('scroll', this.onScroll)
+    this.onShortcutNavigation = this.onShortcutNavigation.bind(this)
+    this.hostElement.addEventListener('keydown', this.onShortcutNavigation)
 
     this.hostBoundingClientRect = this.hostElement.getBoundingClientRect()
     this.mutationObserver = new MutationObserver(this.onBodyMutate.bind(this))
@@ -111,6 +111,7 @@ class BesService {
     if (this.abortController) this.abortController.abort()
     besServices = besServices.filter(item => item !== this)
     this.mutationObserver.disconnect()
+    this.hostElement.removeEventListener('keydown', this.onShortcutNavigation)
     this.hostElement.removeEventListener('scroll', this.onScroll)
     this.hostElement.setAttribute('spellcheck', this.originalSpellcheck)
     this.hostElement.setAttribute('data-gramm', this.originalDataGramm)
@@ -334,11 +335,27 @@ class BesService {
    *
    * @param {Event} e
    */
-  onTab(e) {
+  onShortcutNavigation(e) {
-    if (e.key === 'Tab' && this.highlightElements.length) {
+    if (!this.highlightElements.length) return
+    switch (e.code) {
+      case 'BracketLeft':
+        if (e.ctrlKey) {
+          // Handle Ctrl + [  OR Ctrl + Š
           e.preventDefault()
           e.stopPropagation()
-      this.findNextMistake(e.shiftKey ? -1 : 1)
+          this.findNextMistake(-1)
+        }
+        break
+      case 'BracketRight':
+        if (e.ctrlKey) {
+          // Handle Ctrl + ] OR Ctrl + Đ
+          e.preventDefault()
+          e.stopPropagation()
+          this.findNextMistake(1)
+        }
+        break
+      default:
+        break
     }
   }