Java major mode (#63)

Thanks!

Author: erichonorez

docs/major-mode.md

@@ -85,6 +85,18 @@ Required extensions:
 
 - [Ionide F#](https://marketplace.visualstudio.com/items?itemName=Ionide.Ionide-fsharp)
 
+## Java
+
+Required extensions:
+
+- [Language support for Java ™ for Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=redhat.java)
+- [Debugger for Java](https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-debug)
+- [Test Runner for Java](https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-test)
+
+These extensions are all included in the [Extension Pack for Java](https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-pack).
+
+Documentation: [Java in Visual Studio Code](https://code.visualstudio.com/docs/languages/java)
+
 ## Julia
 
 Required extensions: