feat: allow setting type in external secret to support other than Opaque secrets

[Flydiverny]

Possible solution for #109

Does this require anything more than being able to set type in the external secret resource?

Example:

apiVersion: kubernetes-client.io/v1
kind: ExternalSecret
metadata:
  name: my-dockerhub-secret
secretDescriptor:
  backendType: secretsManager
  type: kubernetes.io/dockerconfigjson
  data:
    - key: /development/mma/dockerhub
      name: .dockerconfigjson

Where the value in backend would be

{"auths":{"https://index.docker.io/v1/":{"auth":"bXljcmVkZW50aWFsczp2ZXJ5LW5pY2UtcGFzc3dvcmQ="}}}

Similarly could be done for tls?

apiVersion: kubernetes-client.io/v1
kind: ExternalSecret
metadata:
  name: my-tls
secretDescriptor:
  backendType: secretsManager
  type: kubernetes.io/tls
  data:
    - key: /development/mma/certifcate
      property: crt
      name: tls.crt
    - key: /development/mma/certifcate
      property: key
      name: tls.key

Originally posted by @Flydiverny in #109 (comment)

[Flydiverny]

@silasbw @jeffpearce Please have a look :D

[jeffpearce]

Kinda a nit, but

Suggested change

	- key: /development/certifcate
	- key: /development/certificate

[jeffpearce]

Suggested change

	- key: /development/certifcate
	- key: /development/certificate

[jeffpearce]

Would you mind adding a test?

[Flydiverny]

@jeffpearce test added and typo fixed 😄

[jeffpearce]

Thanks @Flydiverny !

[eshamay]

I'm not familiar with the release process here, but I'm closely tracking this PR because I have immediate use for it. When is the next release (1.3.2 ?) expected to make it out?

[antoniotamer]

My team is eagerly awaiting this change as well, can we get an ETA on the next release?