adds --description value to the gh command

[zhephyn]

Fixes #4

[zhephyn]

Ended up using shell words to address the issue. However I'm curious if a helper approach would've been better. Something like this:

def shell_escape_single_quote(str)
  "'" + str.gsub("'", "'\\''") + "'"
end

and then this

cmd = "gh repo create --private #{project_config.org_slash_project_kebab} --description #{shell_escape_single_quote(project_config.description)}"

However shell words is not a dependency and comes with ruby itself so maybe it could be fine for use. The helper approach would have been better if maybe by using shell words we were adding a new dependency. wdyt?