Implemented a function to check whether a buffer is saved.
Implemented a function to run a shell command on a selected buffer.
Added a customization group for mallard-mode.
Added customizable variables for document validation.
Implemented a function to validate the currently edited document.
Implemented a function to display the status of the currently edited file.
Implemented a function to display editorial comments in the document.
Implemented a function to check external links in the document.
Added a keymap.
Updated the documentation.
Updated version information.