The "move home and be vim-less" release

• Unpinned Textual. (#50)
• Added local_start_location to the configuration file. (#59)
• Added ctrl+r as an alternative binding for jumping to the document. (#60)
• Added support for scrolling the markdown up/down half a page. (#62)
• Added some movement key bindings to the markdown document that might be familiar to users of things like vim and less. (#63)