docs: add sidebar entry for project API tokens guide (#3602)

It seems that we forgot to add this doc to the sidebar. This PR fixes
that

website/sidebars.js

@@ -69,6 +69,7 @@ module.exports = {
                     items: [
                         'how-to/how-to-create-api-tokens',
                         'how-to/how-to-create-personal-access-tokens',
+                        'how-to/how-to-create-project-api-tokens',
                         'how-to/how-to-create-service-accounts',
                         'how-to/how-to-download-login-history',
                         'how-to/how-to-use-the-admin-api',