docker-mods-java for code-server and openvscode-server

The following versions are available:

• Java 8: add astrosquared/docker-mods-java:code-server-java8 to your mods
• Java 11: use the upstream version
• Java 17: add astrosquared/docker-mods-java:code-server-java17 to your mods
• Java 21: add astrosquared/docker-mods-java:code-server-java21 to your mods

The source code is available on the branch code-server-javaX where X is the Java version number.

Also note that these were only tested on code-server, but should work on openvscode-server.