Provide support for Java 21

Signed-off-by: Snjezana Peco <snjezana.peco@redhat.com>

Author: snjeza

README.md

@@ -24,7 +24,7 @@ Features
 =========
 ![ screencast ](https://raw.githubusercontent.com/redhat-developer/vscode-java/master/images/vscode-java.0.0.1.gif)
 
-* Supports code from Java 1.5 to Java 20
+* Supports code from Java 1.5 to Java 21
 * Maven pom.xml project support
 * Gradle project support (with experimental Android project import support)
 * Standalone Java files support
@@ -81,8 +81,8 @@ If you need to compile your projects against a different JDK version, it's recom
     "path": "/path/to/jdk-11",
   },
   {
-    "name": "JavaSE-20",
-    "path": "/path/to/jdk-20",
+    "name": "JavaSE-21",
+    "path": "/path/to/jdk-21",
     "default": true
   },
 ]

package.json

@@ -806,7 +806,8 @@
                   "JavaSE-17",
                   "JavaSE-18",
                   "JavaSE-19",
-                  "JavaSE-20"
+                  "JavaSE-20",
+                  "JavaSE-21"
                 ],
                 "description": "Java Execution Environment name. Must be unique."
               },