feat(charts): adding extraDeploy key for additional k8s objects

[sc250024]

This adds an extraDeploy key to the chart, enabling users to attach additional Kubernetes manifests to the deployment as needed. The extra-deploy.yaml and render function were lifted from the Bitnami charts, which do the same thing.

• https://github.com/bitnami/charts/blob/03e195bff6757cc3f7ceef76e6179d51d0be8a4e/bitnami/wordpress/templates/extra-list.yaml
• https://github.com/bitnami/charts/blob/03e195bff6757cc3f7ceef76e6179d51d0be8a4e/bitnami/common/templates/_tplvalues.tpl#L7-L24

The reasoning for this is that my company uses a CRD linked with Backstage for ownership over certain components in Kubernetes. For owning this resource, we would need to deploy extra templates alongside this component.

[sc250024]

~~@stefanprodan @aryan9600 Could this be included in the https://github.com/fluxcd/flagger/pull/1788 release?~~

Nevermind