[aws-cloudwatch-metrics] Possibility to add extra envs into container template

[alextarapatin]

Is your feature request related to a problem?
I've encountered a problem when pod has to connect to AWS Cloudwatch through proxy. Chart does not support adding extra container envs for http and https proxy URL's.

Is your feature request related to a specific Helm chart, if yes mention name of the chart?
aws-cloudwatch-metrics

Describe the solution you'd like
able to add extra envs to daemonset chart

Describe alternatives you've considered
Right now I'm running a script, using kubectl set env option, to inject http and https proxy URL variables after deployment. I understand that I could fork the chart and make the appropriate changes myself, but I think an upstream approach would be better.