Generalize Chart specific handling

[JensAc]

The switch here introduces chart specific handling in the code.

gardener-chart-releaser/pkg/releaser/importer.go

Line 107 in 1411030

switch c.Name() {

If we want to avoid quick fixes like those, we should ask upstream, whether correct and unique image tags could be introduced in the upstream charts. Otherwise, changes like this could be generalized and be part of the config, for example.