testing a fix for Frescobaldi lag with big source files

[Federico Bruni]

Hi folks

I'm sure some of you who use Frescobaldi might have experienced the lag 
and slowness of Frescobaldi when working on big files. There's an open 
PR which should alleviate this problem (but the improvement might 
depend on your hardware specs). Would you like to test it?

https://github.com/frescobaldi/frescobaldi/pull/2152

There are testing packages for macOS, Windows and Linux (flatpak), so 
running Frescobaldi from source is not the only option.

Thanks
Federico