Update to add SPLUNK_GENERAL_TERMS env. variable

[GasPar-Sec]

To deploy the recent Splunk container, it is required to accept the Splunk General Terms.
This can be done by adding the following environment variable to the docker run command:

• SPLUNK_GENERAL_TERMS=--accept-sgt-current-at-splunk-com

[pyth0n1c]

Thanks for the PR @GasPar-Sec - I need to determine if this causes an issue when starting pre-10.x containers as well.
If it does NOT cause an issue, then I will merge the PR.
It if DOES cause an issue, then I will have to build a bit of logic to ONLY include this parameter on 10.x+ instances.

For other folks looking at this PR, here is some documentation around this new, required flag:
https://hub.docker.com/r/splunk/splunk#:~:text=Starting%20in%2010.x%20image%20versions%20of%20Splunk%20Enterprise%20and%20Splunk%20Universal%20Forwarder%2C