headline
One line of large display text on a UI stage, coloured run by run by its `spans` (or its `text` in one `color`); it does not wrap, and a `typewriter` or `reveal-clip` channel reveals it.
headline(align=left size=1 weight=1)
Attributes
aligntext`center` centres the line on `x`; anything else starts it at `x` (default `left`).12×sizenumberFont size in stage units (default 64).12×weightnumberFont weight (default 700).12×