enable_paragraphs option not working as intended

[andredelft]

When enabling paragraphs, the following unwanted behaviour is occuring:

>>> leiden_plus('<= Leiden+ section =>', enable_paragraphs=True)
'<ab><p>Leiden+ section </p></ab>'

This should just be <ab>Leiden+ section</ab>.

The problem is that <= and => are formatted as different blocks using preprocessors, and stitched together using postprocessors, rendering the text content as a single paragraph in between by the regular markdown paragraph processor. It's probably better to use a mechanism where <= ... => and <D= ... =D> are interpreted as separate blocks.