Default shell should be set using chsh

[danlamanna]

As of #17 the default shell is set using a VSCode setting instead of changing the shell of the user via chsh (e.g. https://github.com/nils-geistmann/devcontainers-features/blob/712d8a4fc8ad1557eee806864ce726a55da3ed65/src/zsh/install.sh#L17). This makes it difficult for downstream users to override in an automated fashion with something like https://code.visualstudio.com/docs/devcontainers/containers#_personalizing-with-dotfile-repositories.

The context for this is larger projects with multiple developers with different shell preferences. I think this should be resolved via:

1. Adding an option for if fish should be set to the default shell (defaulting to true to preserve backward compatibility)
2. Remove the setting customization
3. Run chsh inside install.sh if the option is set to true

Does this sound reasonable? If so I can file a PR.

[eitsupi]

I am not sure of your use case.
What tool are you trying to use the Dev Container Feature from?

This setting only affects vscode, and I believe the setting in settings.json at the project level takes precedence.

devcontainer-features/src/fish/devcontainer-feature.json

Lines 14 to 20 in 79c3a5b

	"customizations": {
	"vscode": {
	"settings": {
	"terminal.integrated.defaultProfile.linux": "fish"
	}
	}
	},

IIUC, fish is not POSIX shell compatible and may cause problems if set as the default shell.
So I don't think such a change is allowed here.

I would recommend removing the fish Feature for such a large project where only certain users use fish.
Instead, set it to dev.containers.defaultFeatures in VS Code's personal settings so that fish will always be installed.
(You may want to see https://github.com/orgs/devcontainers/discussions/60)