Working on #7. added basic numbered footnote. binding alt+shift+6 (will change)
go to from the footnote definition to the first reference
magic notes: insert, go back to ref and go forward to the definition with the same keybinding
shift+down and shift+up to go and back footnotes
keymaps for win and osx
move view to reference after insert
doc magic footnotes
Merge branch 'footnotes'. This fix #7