Use Asciidoctor's `kbd` macro in Podboat operations overview
Use Asciidoctor's `kbd` macro in Podboat operations overview

Changed from colon-delimited to pipe-delimited to avoid escaping the
colons in the `kbd:[<key>]` macro uses

newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat