Add a Doc note about using the `jwksResolverCA` feature out of TechoPreview

This story is related to https://issues.redhat.com/browse/OSSM-1107

We implemented a new SMCP feild `jwksResolverCA` for supporting upstream `jwksResolverExtraRootCA` parameter.
Changes are implemented in OSSM 2.1.3 SMCP and incoming OSSM 2.2.1 SMCP

Doc Request:

• We can add a resolved issue item in the 2.2.1 and next 2.1.x release note about the
  https://issues.redhat.com/browse/OSSM-1107

• We can add a SMCP example for users who want to configure their own JWKS resolver CA from a SMCP spec. For example,

SMCP spec:

[...]
spec:
  security:
    dataPlane:
        mtls: true # enable mtls for data plane
    # JWKSResolver extra CA
    # PEM-encoded certificate content to trust an additional CA
    jwksResolverCA: |
        -----BEGIN CERTIFICATE-----
        [...]
        [...]
        -----END CERTIFICATE-----
...

Expected behavior:

After applying the above SMCP spec for configuring the JWKS Resolver CA certificate, user should be able to find a ConfigMap such as pilot-jwks-cacerts-<SMCP name> created with the CA .pem data.

For example,

ConfigMap pilot-jwks-cacerts-<SMCP name>

kind: ConfigMap
apiVersion: v1
data:
  extra.pem: |
      -----BEGIN CERTIFICATE-----
      [...]
      [...]
      -----END CERTIFICATE-----