[Feature] Add --dev flag if dependencies can't be found

[mrcjkb]

Some non-dev rocks might have dependencies listed that only exist in the dev manifest.
It might be a good idea to check install errors for dependencies not being found, and re-run with --dev.

I'm not 100 % sure how I feel about this. Ideally, rocks that depend on something unstable shouldn't have stable releases.

[mrcjkb]

I'd propose YAGNI for now.

For reference: This would allow plugins that depend on other plugins that only have an scm release to have a SemVer version.
sindrets/diffview.nvim#320

The question is, should plugins that have unstable dependencies have unstable releases?