Without a margin, things look poor if the last row is blue: it then
merges into the caption at the top of the next table.
I've also added a small border because I think it helps to break things
up a little.
* Configure syntax highlighter to use CSS classes
the inline `style` attributes cause CSP errors (and don't work). Instead, we
can use proper CSS classes.
* Configure response headers for Hugo dev server
make the dev server serve response headers which match the live site, for
better testing.
Now that we've dropped the old build pipeline (and an assets directory does not exist in the repo any longer, we can rename the hugo version of the assets (assets-hugo) created during the build tools migration back to simply assets.
