Add fx components 291-320 and the home scene; Kit.Shot, Kit.Toward

Palette cycling, sky, sun and moon, clouds, starfield, rain, snow,
petals, leaves, fireflies, waterfall, ocean, campfire, lava, aurora,
lightning, mountains and a season scene; scanlines, vignette, screen
shake, flash, dither fades, iris wipes, dissolves, mosaics, glitches,
sparkles, explosions and confetti. Home opens on a live scene in the
palette's season and a strip of all eight palettes.

pixel adds Canvas.Cycled, Sprite.At, SpriteOf, Kit.Toward and
Kit.Shot, which spends a cue under Reduce Motion so it never replays;
display exports Reduce. Gallery grids and the sidebar are one Tab
stop each.

feedback/shake.go

@@ -18,9 +18,6 @@ var shakes = [...]int{2, -2, 2, -2, 1, -1, 0}
 func Shake(c *ui.Context, o ShakeOptions, content func()) *ui.Element {
 	k := pixel.K(c)
 	e := ui.Box(c)
-	dx := 0
-	if step := k.Since(c, k.Cue(e, o.Cue), 20, len(shakes)-1); !k.Reduce() {
-		dx = shakes[step]
-	}
+	dx := shakes[k.Shot(c, e, o.Cue, 20, len(shakes)-1)]
 	return e.Padding(0, k.D(2-dx), 0, k.D(2+dx)).Children(content)
 }