Allow file contents inline in `values.yaml`

Is your feature request related to a problem? Please describe. Due to this issue in the official Helm repository (which I can't believe is a problem since 2017) , it is currently not possible to use/refer files outside the fission Helm Chart directory.

When I want to install fission with kafka mqt (with TLS) enabled, I need to unzip the Chart, move the TLS certificates and keys inside the unzipped directory and install the Helm Chart from the directory.

Describe the solution you'd like I want to be able to put the content of the certificates and the keys inline in the values.yaml instead of referring to a file which must be placed inside the Chart itself.

Describe alternatives you've considered Hack around in our CI/CD: unpack the Chart, move the TLS files into the directory and install this directory as a Chart

Additional context none