* Optional override of runner image in chart
This commit adds the option to override the actions runner image. This
allows running the controller in environments where access to Dockerhub
is restricted.
It uses the parameter [--runner-image](https://github.com/actions-runner-controller/actions-runner-controller/blob/master/main.go#L89) from the controller.
The default value is set as a constant
[here](acb906164b/main.go (L40)).
The default value for the chart is the same.
* Fixing actionsRunner name
... to actionsRunnerRepositoryAndTag for consistency.
* Bumping chart to v0.12.5
There's no reason to create a non-working secret by default. If someone wants to deploy the secrets via the chart they will need to do some config regardless so they might as well also set the create flag
