main/onboard: new aport

Currently we're using matchbox-keyboard as on screen keyboard. However, onboard seems to be a better alternative to, it has auto-show, word suggestions, themes and settings you can choose. So far the best OSK out there on the market.

There are a few minor issue such as word suggestions doesn't work (not sure why, but i assume that onboard doesn't know about the program that was in front of it), sound feedback doesn't work at all due to missing sound despite it exists in /usr/share/sounds/freedesktop/stereo/onboard-key-feedback.oga. Other than that, I haven't found any issue while testing.

Tested on qemu-amd64.

Tested on chuwi-hi10plus, multitouch on keyboard works fine.