Feature/ctgr 21 -- homepage

Homepage template

*  adds a new `nestedColumns()` function; it’s just like the `columns()` function we all know and love, but with the added ability to include a parent’s column-count as context in calculating widths
*  improves markup and styling to page header to allow for in-header CTA button
*  cleans up and extends both the `.cards` and `.media` modules
*  reworks the ornamental/stitched banner used here, on the single article template, and possibly elsewhere