Improve fineliner rendering

[robfox92]

Currently, fineliners are much thicker than the RM2 Web UI export. This PR resolves that:

Before (pdf):

After (pdf):

RM2 Reference PDF:
reference.pdf

[bitmeise]

I know necroing a stalled issue on GitHub is not necessarily considered best practice. But since rmc already improved a lot since March without merging this, I'm wondering if the issue which this PR fixes is not an issue for others.
For me, the fineliner and ballpoint pen (probably more?) are definitely much too thick.

[ricklupton]

Thanks, sorry I haven't replied about this yet -- I haven't checked this again recently, I don't know if anyone else has a view on if these changes are still an improvement?

[Seb-sti1]

With the current version of rmc, on my rm files, it is not perfect but it is "close" to the rm export. Also in #11 it seems to be close to the provided exported pdf from the rM.

Side note: it might be true only for certain pen and not for other. If I have some free time this week i'll try to do a rm with all the pen types and sizes (and post it here)