docs: Update nonroot.md to include how to set the securityContext for the configReloader sidecar

[jessebot]

PR Description

Adds a small section to the example of running as nonroot to include how to run the config reloader sidecar as nonroot.

Which issue(s) this PR fixes

None that I know of.

Notes to the Reviewer

This was something I had to do in order to avoid issues with OPA stopping me from running this helm chart with the config reloader enabled.

PR Checklist

• [ ] CHANGELOG.md updated
• [x] Documentation added

[CLAassistant]

All committers have signed the CLA.

[clayton-cornell]

I've started the test build. @jessebot if you can sign the CLA, I'll be able to get this PR merged.

[dehaansa]

Looks like this needs a rebase/merge from main to fix CI issues.

[clayton-cornell]

@jessebot do you have some time to sign the CLA and do a quick rebase so we can get this PR merged?

[jessebot]

Done and done, sorry about the delay 🙏

[clayton-cornell]

No worries.. just merging today :-)