lang/java: Add file templates

- `__annotation-type`
- `__enum`
- `__interface`
- `__record`
- `__` → `__class` (rename)

modules/editor/file-templates/templates/java-mode/__interface

@@ -0,0 +1,9 @@
+# -*- mode: snippet -*-
+# name: Java interface file template
+# --
+package `(+java-current-package)`;
+
+public interface `(+java-current-class)`
+{
+    $0
+}