BlockNote outputs default styles on save

If you edit and save a page without making any change, the output XWiki syntax contains a bunch of CSS styles:

• for paragraphs, headings and blockquote:

  (% style="color:default;background-color:default;text-align:left" %)
  

• for images:

  data-xwiki-image-style-alignment="start"
  

• for tables:

  (% style="color:default" %)
  |=(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" %)apple|=(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" width="120" %)orange|=(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" %)banana|=(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" %)cherry
  |(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" %)green|(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" %)orange|(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" %)yellow|(% style="color:default;background-color:default;text-align:left" colspan="1" rowspan="1" %)red
  

Ideally BlockNote shouldn't output default styles (that have not been applied explicitly by the user). If that's not possible, then we need to try to filter them out on save.