provide testing support for Edge

[johnml1135]

Currenlty it appears that only Chrome and Firefox are the supported browsers allowed for writing tests using pytest:

dash/dash/testing/plugin.py

Line 24 in 6ee3eee

choices=("Chrome", "Firefox"),

Some corporate environments lock down Chrome at the preference of Edge. having full support for testing with Edge in pytest would be very helpful.

[alexcjohnson]

Good idea! Looks relatively straightforward https://www.geeksforgeeks.org/automated-browser-testing-with-edge-and-selenium-in-python/ and https://developer.microsoft.com/en-us/microsoft-edge/tools/webdriver/

Feel like making a PR to add this? 🙏