Xiaomi Mi Robot Vacuum (v1 only) bumper extension

This hack will prevent your Xiaomi Mi Robot Vacuum v1 (the model with the two-buttons-in-one on the top) from climbing furniture (cantilever chairs) and other obstacles. Climbing will be reduced to relatively flat things and carpets up to about 10mm..

Beware:
- you need to have a printer with a print area of at least 260mm in the diagonal.
- I did not do much testing with the cliff sensor - but I don't think this should be a problem.
- This mod will add some minor noise from the side brush