Document the existence of FlexASIO Fluent

[dechamps]

FlexASIO Fluent is a brand new FlexASIO GUI app by @ramiro-uziel that just came out. I should check it out and link it from FlexASIO docs as an alternative to FlexASIO GUI.

Also: according to its README, FlexASIO Fluent hijacks the FlexASIO GUI registry entry so that it opens as the FlexASIO control panel, which is… arguably not the most polite thing to do. Maybe a cleaner approach could be arranged.

[ramiro-uziel]

Hi. I made it public so some friends could test it for me, so I didn't expect it to reach you yet. The registry edit made it easy for me to test it without having to change FlexASIO for an unfinished (at the time) project. Sorry about that 😅.

Right now I do not know what arrangement would be best. I can make a new registry entry with the install path, like FlexASIO GUI. But the issue is if a user has installed both. Maybe it can prefer FlexASIO GUI as a "legacy editor" and if users want to use FlexASIO Fluent they can uninstall the previous one.