Task runner functionality

[dbohdan]

My (trivial) use of a task runner in the guestbook project has made me realize Joker could be its own task runner. It is a problem for task runners to have a cross-platform, expressive scripting language. For this reason, Task includes a pure-Go Unix shell; just is considering embedding RustPython. Joker would get a head start.

Joker could implement a task runner in a way similar to its linter and formatter. For example, the command line arguments joker --task foo bar 2 baz could run (tasks/foo "bar" "2" "baz") or (tasks/foo "bar" 2 "baz") after loading a file like tasks.joke. Another option like joke --list-tasks could list the functions in the namespace tasks in tasks.joke. One could come up with something for a default task (like make or just without arguments).

To be clear, this is not an "I need this" or "I think others need this" feature request. It is something I thought might be cool to have.

Prior art in Clojure: Babashka includes a task runner. I think it would be best for Joker to use a simple source file for tasks instead.