Set linter and formatter to *only* run when files it works for are
actually detected. Uses moreutils' ifne to detect the status of stdin
before sending an empty string to the test suite.
Added up-to-date install instructions and a simple image to the README.
Added an assets directory to house these things and some notes. Removed
`.gitlab-ci.yml` from being linked to the home directory, it does not
belong there.
Will recursively look for `*.bats` files and run them with bats-core test suite. Simple sample unit tests for existing scripts are included in `.config/shell/rc.d/test`.
