[FIX] Package: ensure we ship style sheets in releases

Ever since we started using external style sheets in addition to our
inline css, we never updated the package.json file to ensure it got
added to the release on npm.

closes #7600

Task: 0
X-original-commit: a61715a
Signed-off-by: Vincent Schippefilt (vsc) <vsc@odoo.com>
Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>

Author: rrahir

package.json

@@ -10,7 +10,8 @@
   "files": [
     "dist/*.js",
     "dist/*.d.ts",
-    "dist/*.xml"
+    "dist/*.xml",
+    "dist/*.css"
   ],
   "scripts": {
     "serve-static": "live-server --open=demo --watch=build/o_spreadsheet.iife.js,build/o_spreadsheet.xml,build/o_spreadsheet.css,main.css,demo",