Docs re: common DOMPDF troubleshooting

- https://cliveportman.co.uk/code/dom-pdf-no-block-level-parent-found-not-good-error-with-or-without-craft-cms
- https://cliveportman.co.uk/code/table-not-displaying-correctly-when-exporting-html-to-pdf-using-dompdf
- https://craftcms.stackexchange.com/questions/27071/printmaker-pdf-includes-odd-spaces-and-blank-page