Move bridge javascript into existing folder structure

app/javascript/helpers/bridge/viewport_helpers.js

@@ -0,0 +1,24 @@
+let top = 0
+const viewportTarget = window.visualViewport || window
+
+export const viewport = {
+  get top() {
+    return top
+  },
+  get height() {
+    return viewportTarget.height || window.innerHeight
+  }
+}
+
+function update() {
+  requestAnimationFrame(() => {
+    const styles = getComputedStyle(document.documentElement)
+    const customInset = styles.getPropertyValue("--custom-safe-inset-top")
+    const fallbackInset = styles.getPropertyValue("--safe-area-inset-top")
+    const insetValue = (customInset || fallbackInset).trim()
+    top = parseInt(insetValue || "0", 10) || 0
+  })
+}
+
+viewportTarget.addEventListener("resize", update)
+update()