uses the <tool-tip> tag now, and the setupTooltips() function in ui.ts
must be called at any point in the pages load. added "below-center"
position, showing below and centered horizontally. breakpoint tailwind
lingo also now works (e.g. "below-center sm:right"). If a left or
right-aligned tooltip clips off the screen, it will be shifted the
appropriate amount left/right to avoid that automatically.
Harvey Tindall