feat: get query parameters for preview

* add a custom hook for grabbing query parameters off the location
  object
* use hook in preview page to grab and log out the 'pr' and 'quickstart'
  query parameters

src/hooks/useQueryParameter.js

@@ -0,0 +1,20 @@
+import { useEffect, useState } from 'react';
+
+/**
+ * A hook to grab query parameters off of the current URL
+ * @param {string} parameterKey - The key for the query parameter
+ * @param {object} location - The Gatsby location object
+ * @returns {string|null} The string value of the parameter or null if it does not exist
+ */
+const useQueryParameter = (parameterKey, location) => {
+  const [param, setParam] = useState(null);
+
+  useEffect(() => {
+    const urlParams = new URLSearchParams(location.search);
+    setParam(urlParams.get(parameterKey));
+  }, [parameterKey, location]);
+
+  return param;
+};
+
+export default useQueryParameter;

src/pages/preview.js

@@ -0,0 +1,17 @@
+import PropTypes from 'prop-types';
+import useQueryParameter from '../hooks/useQueryParameter';
+
+const PreviewPage = ({ location }) => {
+  const prNumber = useQueryParameter('pr', location);
+  const quickstartPath = useQueryParameter('quickstart', location);
+
+  console.log(prNumber);
+  console.log(quickstartPath);
+  return <span>oh hai</span>;
+};
+
+PreviewPage.propTypes = {
+  location: PropTypes.object.isRequired,
+};
+
+export default PreviewPage;