Mellow FLY-ADXL345-USB mounts

Here are a couple of mounts for Mellow's Raspberry Pi Pico-based ADXL345 accelerometer, the FLY-ADXL345-USB.

One mounts to the BLTouch bracket on the Ender 5 Plus; that's all that's required for the Ender 5 Plus, as the one accelerometer can read both X and Y axes in this location.

Another mounts to the BLTouch mounting points on the Ender 3 V2 - I use the KlackEnder setup which leaves the BLTouch mounts free. The final mount is for the bed on a bedslinger like the Ender 3 V2. This lets a user install two FLY-ADXL345-USB devices, with appropriate configuration under Klipper, to calibrate X and Y axes at the same time.

Additionally, the bed mount has wings so that it can be reused with the bed clamps that I have.

When printing the bed mount consider the USB cable path; also, while it's probably best to have the bed mount in the middle of the buildplate, consider whether the bed mount will stop the printer from homing if located in the middle of the buildplate.