fix(pdf): area highlights don't blink

Area highlights don't blink when jumping to it.  

Maybe we could unify the id naming style of all highlights elements. So, area highlights will blink as text highlights do.

- `id` of text highlight: 27e3b9d019/src/main/frontend/extensions/pdf/core.cljs (L254)

- [The part for blinking](27e3b9d019/src/main/frontend/extensions/pdf/utils.js (L123C5-L130)) in `pdf/utils.js` 
``` js
  // blink highlight
  function blinkHighlight () {
    const id = highlight?.id
    const el = document.getElementById(`hl_${id}`)
    if (!el) return
    el.classList.add('hl-flash')
    setTimeout(() => el?.classList.remove('hl-flash'), 1200)
  }
```  
PS: I don't know if disabling the blinking is by design. Let me know if it's not a bug but a feature :)

src/main/frontend/extensions/pdf/core.cljs

@@ -371,7 +371,7 @@
     (when-let [vw-bounding (get-in vw-hl [:position :bounding])]
       (let [{:keys [color]} (:properties hl)]
         [:div.extensions__pdf-hls-area-region
-         {:id              id
+         {:id              (str "hl_" id)
           :ref             *el
           :style           vw-bounding
           :data-color      color