ESP32-Presense - ESP32-Devkit case with ventilation slots

This is a remix of the case from @regularfry. 

I just added some vents because the ESP32 gets quite warm when running as with the Espresense firmware.

Here is the description of @regularfry, which is also true for me:

I'm using these esp32-devkit boards as ESPresense sensors.

I just wanted a box I could put them in so I didn't have bare electronics around the house, and I couldn't be bothered ordering some without header pins.  At the moment I'm just taping them to the back of old phone chargers and plugging them into the mains.

The box lets you get at the USB port (obviously, for power) but you need to take the lid off to get to the reset button.  Some chargers have plugs that are slim enough to do this but others don't.  I've not yet had a problem which needed me to fix that.

To pre-empt commentary: yes, these cases have no ventilation.  In my use case they get slightly warm to the touch, but nowhere near hot enough for me to worry about the plastic or the electronics. ESPresense barely makes them break a sweat.

These cases are a tight enough fit for the boards that they don't need any fixtures.  The slide-fit lid keeps things in place.