chore: add engines field to package.json (#379)

Specify minimum Node.js version requirement (>=20.0.0) in
package.json to prevent build issues for contributors using
incompatible Node.js versions.

Closes #367

Author: okxint

package.json

@@ -37,5 +37,8 @@
   "bugs": {
     "url": "https://github.com/NextCommunity/NextCommunity.github.io/issues"
   },
-  "homepage": "https://github.com/NextCommunity/NextCommunity.github.io#readme"
+  "homepage": "https://github.com/NextCommunity/NextCommunity.github.io#readme",
+  "engines": {
+    "node": ">=20.0.0"
+  }
 }