No way to keep going if one subcommand fails

What GNU Make offers is a command line switch `-k`, or `--keep-going`. What this switch does is it carries on with the build even if one of the dependent makefile targets fails.

I have a justfile containing various long-running tests, and there is also a `test` target having `test1`, `test2`, `test3` as dependants. I am using this top-level targets to have all the tests run overnight or over a weekend. So it would be great if I could supply a command line flag to run all three tests, even if one fails. I don't see any mention of such an option in the helptext, apologies if I missed it!

I'm proposing something like `just -k tests`, or `just --keep-going tests`, in the heritage of what GNU Make does, but feel free to propose a different name or an entirely different solution (like an environment variable?)

Is this something you'd accept a pull request for?

No files or tests are named. Start by reading the existing command-line help and the target-dependency execution behavior, then determine how a `-k` or `--keep-going` option should handle failed dependencies. Done means the chosen behavior is implemented, documented in help text, and verified for a target with multiple dependants.

Written by the indexing model from the issue text.