chore: automatically bundle external assets on install

when installing the project by just reading the docs, assets are not
generated after launching the app for the first time. Now they are and
marking this as postinstall ensures we always get the correct build
after dependencies updates

installation.md

@@ -26,6 +26,9 @@ This guide provides steps to run the MonComptePro Node.js application locally wh
    npm install
    ```
 
+   Note: this will also build required JS and CSS assets of dependencies and add them in the `public/` dir.
+   You can build those assets again at anytime with the `npm run build:assets` command.
+
 2. **Create a local version of dotenv file**: Inside the project's root directory, run:
 
    ```bash

package.json

@@ -6,12 +6,14 @@
     "node": "16.20.2"
   },
   "scripts": {
+    "postinstall": "npm run build:assets",
     "lint": "prettier --write */*.ts",
     "start": "node build/index.js",
     "dev": "concurrently \"npm:watch:*\"",
     "build": "run-s build:**",
     "build:typescript": "tsc",
     "build:views": "bash -c 'cp -r src/views build/views'",
+    "build:assets": "run-s build:assets:**",
     "build:assets:simplewebauthn": "bash -c 'cp node_modules/@simplewebauthn/browser/dist/bundle/index.umd.min.js public/simplewebauthn.umd.min.js'",
     "build:assets:choicesjs": "bash -c 'cp node_modules/choices.js/public/assets/{scripts/choices.min.js,styles/choices.min.css} public/'",
     "build:assets:dsfr": "bash -c 'cp -r node_modules/@gouvfr/dsfr/dist/{dsfr.min.css,fonts,icons,utility} public/'",