refactor: import rollup

src/util/http.js

@@ -0,0 +1,17 @@
+export function get (url) {
+  return new Promise((resolve, reject) => {
+    const xhr = new XMLHttpRequest()
+    xhr.onload = () => {
+      if (xhr.status >= 200 && xhr.status < 300) {
+        resolve(xhr.responseText)
+      } else {
+        reject(new Error(xhr.statusText))
+      }
+    }
+    xhr.onerror = () => {
+      reject(new Error('An error occurred whilst sending the response.'))
+    }
+    xhr.open('GET', url)
+    xhr.send()
+  })
+}