Helmfile has been providing a feature called "adhoc chart dependency" that basially enabled you to add Chart.yaml `dependencies` entry adhocly without forking or modifying the chart.
It was missing the support for using a local chart as the adhoc dependency. This patch adds that.
Usage:
`releases[].dependencies[].chart` is enhanced to accept the fs path to the local chart:
```
releases:
- name: foo
chart: ./path/to/foo
dependencies:
- chart: ./path/to/bar
```
Resolves#1762