Adding Image Pull Secret to Helm Chart

[robrankin]

Description

Adding Image Pull Secret to the chart, so we can use private repositories.

Checklist

• I have reviewed the contributing guidelines.
• I have included unit tests for my changes or additions.
• I have successfully run make test-docker with my changes.
• I have updated the documentation.
• I have updated the changelog.

Questions or Comments

[lepouletsuisse]

I think this PR is linked to this discussion.
However, I think it is still a good idea to be able to set the imagePullSecrets on the deployment itself

[jertel]

I agree. Will merge once the changelog is updated. I'll update it myself if no one else gets to it this week.

[robrankin]

Updated the changelog. Anything else needed?

[jertel]

Thank you! Also check that other thread @lepouletsuisse mentioned in case it might be simpler if your deployments all use the same private image repo.