attempt to better document Simplify traits `epsilon` parameter

[michaelkirk]

• [x] I agree to follow the project's code of conduct.

• [n/a] I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

I'm actually not sure if this is what the parameter really means, but it's my best guess at this point. Is anyone more familiar willing to clarify?

[urschrei]

The triangle explanation (which is correct!) only applies to the Visvalingam-Whyatt algorithm. The RDP algorithm (which underlies Simplify) is distance-based…

[michaelkirk]

Thank you! Please take another look @urschrei