Add page numbers for PDF rendition with WeasyPrint
Highlights in this release:
* Allow PDF rendition with WeasyPrint
tpnote --export=- mydoc.md | weasyprint - mydoc.pdf
* Refactor `tmpl_html` templates
* Disable library logging when invoking with `--debug <LEVEL>`
* Remove some workaround for early versions of the `notify` crate.
* Bug fix: source also `tmpl_html` section when given in a configuration file