[#40] Filtering option for weasyprint output to find relevant messages

[kreuzberger]

The output of weasyprint has many non relevant informations and errors about css file the user cannot change. To see relevant messages from users css and document, the output could be filtered by given filter string to reduce amount of messages in the IDE

[danwos]

That's a great feature, thanks for the PR :+1:

[danwos]

Oh the branch has some conflicts, mostly because such merged some other PRs before. I will merge it as soon as these are fixed.