[FR] Allow for a config file to always supply options that you don't expect to change

[jessesimpson36]

Describe the use case:

Some developers only work on one helm chart, and it may be cumbersome to type out the parameters

helm yamldiff default_values.yaml supplied_values.yaml -o output.yaml

If you know the helm chart you're working in, maybe you want to supply a version number instead.

helm yamldiff --chart bitnami/postgresql --version 1.0.2  supplied_values.yaml

And maybe you might have a config file in ~/.config/yamldiff/config.yaml

chart: bitnami/postgresql

then you only supply

helm yamldiff --version 1.0.2 supplied_values.yaml