add plugin and fix example

editor/vscode-jdg/README.md

@@ -0,0 +1,29 @@
+# Judge DSL — VS Code extension
+
+Syntax highlighting for `.jdg` files (the judge test-suite DSL).
+
+## Install (local, no marketplace)
+
+### VS Code
+
+Copy this directory into your extensions folder — VS Code loads it on next
+restart:
+
+```sh
+# VS Code
+cp -r editor/vscode-jdg ~/.vscode/extensions/jdg-language-0.1.0
+```
+
+Restart the editor, open any `.jdg` file — you should see keywords, strings,
+durations highlighted.
+
+### Package as `.vsix` (shareable)
+
+```sh
+npm install -g @vscode/vsce
+cd editor/vscode-jdg
+vsce package
+# → jdg-language-0.1.0.vsix
+```
+
+Then in VS Code: `Extensions` → `...` → `Install from VSIX`.