Clarify that oscilloscope attenuation is virtual

[MatthewSteeves]

Upon learning what attenuation was for oscilloscope probes, I wrongly believed that since Labrador offered a 10x attenuation setting in the GUI, I could set it to 10x and then be able to measure voltages up to 200V (10x the Labrador's max of ~20V)!

Good thing I looked at the schematic and searched through Github and saw the requests where virtual attenuation was requested. :)

Since Labrador's target market seems to include relative beginners such as myself, perhaps a word of caution/clarification would be helpful. Locations to consider:
In the Wiki/Guide (whick doesn't mention the attenuation setting at all).
As a (popup) upon selecting a non-1x attentuation setting. (With "don't show again" checkbox)

Thoughts?