[translations] catalan strings in scripts/build/create-weblinks-itexi.py

[Federico Bruni <fedelogy@xxxxxxxxx>]

Hi Walter

I see that 'make doc' is printing some warnings about missing catalan translations in scripts/build/create-weblinks-itexi.py:

/usr/bin/python -tt /home/fede/lilypond-git/scripts/build/create-weblinks-itexi.py > out/weblinks.itexi
create-weblinks-itexi: warning: [ca]: translation missing for: Source
create-weblinks-itexi: warning: [ca]: translation missing for: Source
create-weblinks-itexi: warning: [ca]: translation missing for: Notation
[...]

This is not mentioned in the Contributor Guide.. Could you please translate those strings?

Thank you

Federico