documentation updates

Author: xzel23

doc/introduction.adoc

@@ -20,7 +20,7 @@ and a `runtimeZip` task that additionally creates a zip archive of the custom ru
 In addition, a `suggestModules` task helps you choose the modules to include in your custom JRE.
 With the `jpackage` task you can create a platform-specific installer for your application.
 
-WARNING: The plugin requires Java 11 and Gradle 7.0 or newer.
+WARNING: The plugin requires Java 17 and Gradle 7.4 or newer.
 While it might work with some combinations of older Java and Gradle versions, these are not officially supported.
 If you are forced to work with an older Gradle release, you should use https://badass-runtime-plugin.beryx.org/releases/1.12.7/[the version 1.12.7] of this plugin.
 

doc/user_guide.adoc

@@ -5,6 +5,7 @@ This plugin works with non-modular applications, that is, applications that run
 don't make use of module descriptors.
 Nevertheless, in order to use this plugin, your non-modular application must be compatible with the Java version
 of your target JRE (11 or newer).
+Java 17 is needed to run the current version of this plugin. Use version 1.x of this plugin for older Java versions.
 
 
 == Tasks