Enable using gatsby-plugin-google-gtag in develop via a plugin option

[cameronbraid]

I wish to debug a complex ga integation and having to build/serve to debug is a real pain.

I have a separate gtag tracking code defined for my development environment so I would like an option to configure gatsby-plugin-google-gtag to work in develop mode

[cameronbraid]

As a workaround you can use https://github.com/ds300/patch-package

With the following patch :

gatsby-plugin-google-gtag+3.3.0.patch

diff --git a/node_modules/gatsby-plugin-google-gtag/gatsby-browser.js b/node_modules/gatsby-plugin-google-gtag/gatsby-browser.js
index eae4533..6b63bd9 100644
--- a/node_modules/gatsby-plugin-google-gtag/gatsby-browser.js
+++ b/node_modules/gatsby-plugin-google-gtag/gatsby-browser.js
@@ -3,7 +3,7 @@
 exports.onRouteUpdate = function (_ref) {
   var location = _ref.location;
 
-  if (process.env.NODE_ENV !== "production" || typeof gtag !== "function") {
+  if (typeof gtag !== "function") {
     return null;
   }
 
diff --git a/node_modules/gatsby-plugin-google-gtag/gatsby-ssr.js b/node_modules/gatsby-plugin-google-gtag/gatsby-ssr.js
index 888d237..c9232b5 100644
--- a/node_modules/gatsby-plugin-google-gtag/gatsby-ssr.js
+++ b/node_modules/gatsby-plugin-google-gtag/gatsby-ssr.js
@@ -9,7 +9,7 @@ var _minimatch = require("minimatch");
 exports.onRenderBody = function (_ref, pluginOptions) {
   var setHeadComponents = _ref.setHeadComponents,
       setPostBodyComponents = _ref.setPostBodyComponents;
-  if (process.env.NODE_ENV !== "production" && process.env.NODE_ENV !== "test") return null; // Lighthouse recommends pre-connecting to google analytics
+  // Lighthouse recommends pre-connecting to google analytics
 
   setHeadComponents([/*#__PURE__*/_react.default.createElement("link", {
     rel: "preconnect dns-prefetch",