Circal: First Layer Z-offset Calibration Circle

TL;DR: 35mm diameter circle with text inside similar to a Benchy

This model provides is a simple but fast and effective first layer calibration method. The model is 0.2mm tall so at layer height of 0.2mm it will print just 1 layer.

# Features
- Circles (generally better than squares for calibration since they engage both X and Y axes simultaneously)
- Diameter of 35mm (each circle prints in just ~2 minutes)
- 2 circle options without and with text (Similar to a Benchy's first layer text but much faster to print)

# Instructions
Each circle takes about 2 minutes to print, so you can place several circles around the build plate when you are slicing the model.

### For Z-offset calibration
Start with a low number of circles. During the print, change the z-offset for each circle and make note the z-offset value that was used for each circle.
After the circles are printed remove from the bed and compare the first layer to find the ideal z-offset.

- The lines that make u