Add Fullscreen in viewer, Track links with Google Analytics, Use .env file

- Fullscreen is a component that watches a store value set by the Carousel component on a picture click
- Use a .env file for API and website related settings and informations
- Google Analytics is now in place, tracking each routes link and viewer photo change

package.json

@@ -37,6 +37,7 @@
     "@rollup/plugin-replace": "^2.3.1",
     "autoprefixer": "^9.7.5",
     "babel-plugin-module-resolver": "^4.0.0",
+    "dotenv": "^8.2.0",
     "eslint-config-standard": "^14.1.1",
     "eslint-plugin-import": "^2.20.1",
     "eslint-plugin-node": "^11.0.0",