add a script for generating pngs of snippets
generate-pngs: setup lily build system if necessary
adjusting-horizontal-spacing: add todo
adjusting-horizontal-spacing: change example to something more interesting
preview-mode: add a description and list of future features
todo: add new category.
Update README.md

Don't undermine the position of LSR and don't use "we" which may
sound like i'm talking in the name of whole LilyPond project.
Update adjusting-horizontal-spacing.ly

*Change overridden property to 'common-shortest-duration
*Change name of function
*Add example showing tighter spacing
*Add documentation for function
adjusting-spacing: change interface and name

The function no longer takes a moment as it's argument,
but an ordinary number. This should make it more user-friendly.

I've changed name because when it was a noun it sounded like
a name of a property that should be overridden, rather than
a function name.
adjusting-spacing: fix special character
adjusting-spacing: add predefined commands
adjusting-spacing: add documentation. status=official
adjusting-spacing: separate usage example with a comment.
adjusting-spacing: add usage example with explicit factor.
adjusting-spacing: re-add 'usage example' separator
adjusting-spacing: 'downgrade' to 2.16.2
adjusting-spacing: add some tags
Update preview-mode.md
voice-colors: color rests
add display-grob-anchors