accessibility-enhancement/beforematch/hidden=until-found (#421)

* Added event listener for 'beforematch' to expand accordion and updated hidden from true to 'until-found' making collapsed content accessible

* Update _accordion.scss

src/components/accordion/_accordion.scss

@@ -118,6 +118,10 @@
     }
   }
 
+  &__content[hidden='until-found'] {
+    padding: 0;
+  }
+
   &__content {
     padding: rem(16px);
   }

src/components/accordion/accordion.js

@@ -55,7 +55,7 @@ class Accordion {
 
       if (contentElem) {
         contentElem.id = buttonElem.getAttribute('aria-controls')
-        contentElem.hidden = true
+        contentElem.hidden = 'until-found'
         this.content.push(contentElem)
       }
 
@@ -73,6 +73,7 @@ class Accordion {
   controls() {
     this.buttons.forEach((element) => {
       element.addEventListener('click', this.toggleEvent, false)
+      element.addEventListener('beforematch', this.toggleEvent, false)
     })
     if (this.expandAllBtn && this.collapseAllBtn) {
       this.expandAllBtn.addEventListener('click', this.expandAllEvent, false)
@@ -95,25 +96,26 @@ class Accordion {
     } else if (state === 'close') {
       element.classList.remove('active')
       element.setAttribute('aria-expanded', 'false')
-      targetContent.hidden = true
+      targetContent.hidden = 'until-found'
     }
   }
 
   toggle(event) {
     const { currentTarget } = event
     const targetContent = this.getTargetContent(currentTarget)
+
     if (targetContent) {
       const isHidden = targetContent.hidden
 
-      if ((isHidden)) {
+      if ((isHidden === true) || (isHidden === 'until-found')) {
         this.setAccordionState(currentTarget, 'open')
       } else {
         this.setAccordionState(currentTarget, 'close')
       }
 
       if (this.expandAllBtn && this.collapseAllBtn) {
         this.expandAllBtn.disabled = this.content.every((item) => item.hidden === false)
-        this.collapseAllBtn.disabled = this.content.every((item) => item.hidden === true)
+        this.collapseAllBtn.disabled = this.content.every((item) => item.hidden === 'until-found')
       }
     }
   }