doc: add recommendations about resource limits optimizations (#5276)

* doc: add recommendations about resource limits optimizations

Signed-off-by: Camila Macedo <cmacedo@redhat.com>

* address suggestions nits

Signed-off-by: Camila Macedo <cmacedo@redhat.com>

website/content/en/docs/best-practices/common-recommendation.md

@@ -50,6 +50,8 @@ spec:
     - For Ansible-based operators, you can also use [Molecule][molecule], an Ansible testing framework. For further information see [Testing with Molecule][molecule-tests]
     - For Helm-based operators, you can also use [Chart tests][helm-chart-tests]
 - Ensure that you checked the [Can I customize the projects initialized with operator-sdk?][faq] and understand the [Project Layout][project-layout] before starting to do your customizations as please you on top.
+- Optimize manager resource values in `config/manager/manager.yaml` according to project requirements. It is recommended to define resources limits in order to follow good practices and for security reasons. More info: [Managing Resources for Containers][k8s-manage-resources] and [Docker Security Cheat Sheet][docker-cheats].
+- Look for `TODO(user)` in the source code generated by the CLI to ensure that you follow all suggested customizations.
 - If you will integrate your project with OLM then, also check its [Best Practices][olm-best-practices] section.
 
 [env-test]: https://pkg.go.dev/sigs.k8s.io/controller-runtime/pkg/envtest
@@ -69,3 +71,5 @@ spec:
 [molecule-tests]: /docs/building-operators/ansible/testing-guide
 [helm-chart-tests]: https://helm.sh/docs/topics/chart_tests/
 [envtest]: https://pkg.go.dev/sigs.k8s.io/controller-runtime/pkg/envtest
+[docker-cheats]: https://cheatsheetseries.owasp.org/cheatsheets/Docker_Security_Cheat_Sheet.html#rule-7-limit-resources-memory-cpu-file-descriptors-processes-restarts
+[k8s-manage-resources]: https://kubernetes.io/docs/concepts/configuration/manage-resources-containers/