* a2query: update link to Debian manpage
* check-support-status: update link to Debian manpage
* dpkg-deb: update link to Debian manpage
* dpkg: update link to Debian manpage
* netselect-apt: update link to Debian manpage
* reportbug: update link to Debian manpage
Add example for listing package contents of a downloaded `.deb` file, because `dpkg -L` only works with the `apt` name of the package (and only when installed).