using JMeter 5.4, Helm3, allowing additional volume, etc.,

[mookkiah]

Hi @pedrocesar-ti,

I would like to thank for your effort.

In this pull request I have combined following changes to upgrade and suggest some improvements.

• Using JMeter 5.4
• Document for providing option to supply jks or ignore ssl
• Bringing the helm chart contribution from https://github.com/helm/charts
• Allowing to provide volume and volume mounts so that we can let the users to mount
• Adding documentation to help users with questions like https://github.com/pedrocesar-ti/distributed-jmeter-docker/issues/2
• Removed the old way of getting extra plugins from dockerfile

Thanks, Mahendran.