make the annotation key prefix configurable (#157)

This is intended to make the prefix configurable for projects using this
controller which are not in the Argo ecosystem. This allows such projects
to use an annotation key that is consistent with the conventions of
their project.

Signed-off-by: Your <sdowell@google.com>

feat: support for Google Chat (#49)

feat: support for Google Chat  (#49)

Signed-off-by: Francílio Araújo <francilioaraujo@gmail.com>

* fix: enables to use stringData from local secret

feat: WithAdditionalDestinations with WithAlterDestinations to suppor…

…t removing destinations (#15)

Signed-off-by: Alexander Matyushentsev <AMatyushentsev@gmail.com>

Initial commit

Signed-off-by: Alexander Matyushentsev <AMatyushentsev@gmail.com>