feat: create npm package

package.json

 {
-  "name": "slidev-theme-alpaga",
-  "version": "0.1.0",
+  "name": "@lydra/slidev-theme-alpaga",
+  "version": "0.0.1",
+  "description": "Alpaga is a simple and quick to set up theme for [Slidev](https://github.com/slidevjs/slidev). It's ideal for Markdown notes, booklets or cheatsheets as you can easily customize it to your business colors and identity and export to PDF.",
   "authors": [
     "Celeste Robert",
     "Lydra.fr"
@@ -13,6 +14,13 @@
     "alpaga-theme",
     "theme"
   ],
+  "main": "index.js",
+  "repository": {
+    "type": "git",
+    "url": "git@lab.frogg.it:lydra/www/slidev-theme-alpaga.git"
+  },
+  "license": "GPL-3.0-or-later",
+
   "engines": {
     "node": ">=14.0.0",
     "slidev": ">=0.19.3"