Hotbed for Microcube

Add an heated bed to your microcube, to improve bed tickness for PLA, and allow it to print PETG, and more (maybe ABS if your heater patch is powerfull enough to reach 110°C).

**Beware: An heating bed require a lot a power. You MUST ensure your power supply is strong enough. The printer alone need at least 60W (says 70W for safety). You power supply must be 70W _PLUS_ the Watt power of the heating patch you will be using (plus another safety margin, to be sure).** I'm using a 120W power suppl