Possibility to exclude configmap

[mkindalov]

In our case we would like to manage the ConfigMap "name: {{ template "app.name" . }}-config" using an external tool. ex Terraform. This is difficult at the moment because both terraform and helm are trying to manage the same resource.

The idea is to make the rendering of this ConfigMap optional.
enableConnectorsConfigMap: [true | false] value was added to the values. The default value ensures that the helm chart will continue to work as before after this change.

About the naming of the value field.
I thought it is better to go with "Enable" instead of "Omit" or "Exclude"

More streamlined approach would be:
connectorsConfigMap:
enabled: true
connectors: []

ref: https://github.com/prometheus-msteams/prometheus-msteams#customise-messages-per-ms-teams-channel

connectorsWithCustomTemplates: []

but that would mean that the chart will lose the backwards compatibility. In my opinion its not worth it :)

If you have any suggestions I am happy to rework the PR.