mobile-config-prefs.js: declare touch density

We are on a mobile device.

(This is cherry-picked from an older MR !53 (closed) that was closed with the gitlab move.)

It will likely not fix gnumdk's problem on Debian, but maybe help elsewhere.

approved this merge request

Thanks Cédric and Peter!

added 2 commits

• 7ca5d93a - 1 commit from branch postmarketOS:master
• db629cc4 - mobile-config-prefs.js: enable touch density (MR 57)

Compare with previous version

merged

mentioned in merge request !69 (merged)