chore: bump package.json version

package.json

 {
   "name": "kartenaale-card-templates",
-  "version": "3.0.0",
+  "version": "4.0.0",
   "description": "HTML and data for Anki cards",
   "repository": "https://gitlab.phaidra.org/kartenaale/card-templates",
   "author": "Philipp Stadler <hello@phstadler.com>",