Suggestion: On runScriptLast, default to behavior of runScript if no script has been executed yet

[kevinferretti]

When I use npm-script.rerun-last-script, it brings up the script options if I have not yet executed one.

When I use yarn-script.runScriptLast, it will just send the error message "No script executed yet"

I would like it if this behavior was made to be like the npm version.