Install Webpack "bundle analyzer" and "Git revision" plugin packages

Installed the first Webpack (1) plugins:

- "webpack-bundle-analyzer" (2) - Visualizes the size of Webpack output
  files with an interactive zoomable treemap.
- "git-revision-webpack-plugin" - Generates VERSION and COMMITHASH files
  during build based on a local Git repository.

References:
  (1) https://webpack.js.org
  (2) https://www.npmjs.com/package/git-revision-webpack-plugin
  (3) https://www.npmjs.com/package/webpack-bundle-analyzer

GH-31

package.json

@@ -55,12 +55,14 @@
     "eslint-plugin-jsx-a11y": "6.1.2",
     "eslint-plugin-prettier": "3.0.0",
     "eslint-plugin-react": "7.11.1",
+    "git-revision-webpack-plugin": "3.0.3",
     "husky": "1.1.4",
     "lint-staged": "8.0.5",
     "npm-run-all": "4.1.3",
     "prettier": "1.15.2",
     "remark-cli": "6.0.1",
-    "remark-preset-lint-arcticicestudio": ">=0.2.0 <1.0.0"
+    "remark-preset-lint-arcticicestudio": ">=0.2.0 <1.0.0",
+    "webpack-bundle-analyzer": "3.0.3"
   },
   "dependencies": {
     "gatsby": "2.0.50",