Flight Speed Changer

updated to 1.21.5 and 1.21.6

Added support for 1.21.5

Support for 1.21.4

Support added for 1.21.2 and 1.21.3 but 1.21.3 has not been tested

Now supports JAVA_17 and version below 1.20.6

Flight Speed Changer intial release

Tested on 1.20.6 1.21 1.21.1