docs(AppSettings): clarifies that AppSettings do not propagate
docs(AppSettings): clarifies that AppSettings do not propagate

Closes #429

clap-rs/clap,sru/clap-rs,kbknapp/clap-rs,clap-rs/clap,clap-rs/clap,kbknapp/clap-rs,sru/clap-rs,sru/clap-rs