Ability to detect if WLED app is opening URL

[dkulp]

FPP has a bunch of the WLED effects built in and they can be triggered via special effect pages in the FPP UI. It would be great if the normal WLED App could be used so users could use something they are familiar with. We can easily mimic the detection and the main commands via stuff in the /win and /json directories. Thus, the FPP instances can appear in the main list. However, when the user presses on the instance it goes directly to the main index page (normal for WLED) which would not be appropriate for this. What I was hoping to do is find a way to detect that it's WLED opening the page and redirect it to the appropriate page in the FPP UI dedicated to the WLED effects. I was hoping cookies set on the returns from the /win calls would be carried over, but they aren't (page is opened in the UI browser which is not used for the /win calls). Alternatively, if the user agent had WLED or something (like the /win calls), then we could do the redirect based on that.