feat(helm): add value to customise interactive session images (#795)

[mdonadoni]

Closes reanahub/reana-workflow-controller#569

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 19.22%. Comparing base (f1291ed) to head (cd94d12).

Additional details and impacted files

[](https://app.codecov.io/gh/reanahub/reana/pull/795?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=reanahub) ```diff @@ Coverage Diff @@ ## master #795 +/- ## ======================================= Coverage 19.22% 19.22% ======================================= Files 26 26 Lines 2512 2512 ======================================= Hits 483 483 Misses 2029 2029 ```