Streamlined eslint usage for eslint9 w/ cds8 (#719)

* Streamlined eslint usage

* import from @sap/cds instead of @sap/cds/lib

* Using @sap/cds/eslint.js

* eslint.config.mjs aktualisieren

* Adjusted eslint usage for eslint9 with cds8

bookshop/app/vue/app.js

@@ -77,7 +77,7 @@ function csrfToken (request) {
         document.csrfToken = token
         request.headers['x-csrf-token'] = document.csrfToken
         return request
-    }).catch(_ => {
+    }).catch(() => {
         document.csrfToken = null // set mark to not try again
         return request
     })