Cetz renderer support

[PgBiel]

Inspired by the tabley project by Discord user RubixDev, we could have a "rendering backend" using cetz. This would allow referencing the cells' positions from within cetz. For instance, the table could be assigned a cetz-name: "tb", and then you'd be able to refer to the coordinates of the cell at (2, 1) as "tb-2-1" (third column, second row). Could be useful to e.g. add annotations to tables.

Such a table, however, probably wouldn't be breakable across pages in principle, but that is a limitation to investigate.