Deploy pkgdown website #16

To do

• Re-enable the pkgdown job in ci.yaml
• Update the branch triggers to the agreed build branch (develop or main)
• Set url: https://rivm-syso.github.io/ROvis.table/ in _pkgdown.yml
• Add the site to URL: in DESCRIPTION
• Check that GitHub Pages is enabled with gh-pages as the source
• Confirm the site loads and the badges still work