Add value option to define schedulerName (#150)

For those who have a need to configure the schedulerName like us, make this an option just as it is for example in the postgres chart

Co-authored-by: Dimitri Ars <dimitri.ars@kpn.com>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/150
Reviewed-by: luhahn <luhahn@noreply.gitea.io>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: mrdima <mrdima@noreply.gitea.io>
Co-committed-by: mrdima <mrdima@noreply.gitea.io>

values.yaml

@@ -68,6 +68,11 @@ resources: {}
   #   cpu: 100m
   #   memory: 128Mi
 
+## Use an alternate scheduler, e.g. "stork".
+## ref: https://kubernetes.io/docs/tasks/administer-cluster/configure-multiple-schedulers/
+##
+# schedulerName:
+
 nodeSelector: {}
 
 tolerations: []