Fix debugging not working

VSCode was not able to find the original source of the bundled
extension because it was looking for the source in the `out` directory.
By setting the `sourceRoot` to the `extensions/ql-vscode` directory
which is located at `..` from the `out` directory, VSCode is able to
find the original source and breakpoints are hit.

extensions/ql-vscode/gulpfile.ts/typescript.ts

@@ -46,6 +46,7 @@ export function compileEsbuild() {
         platform: "node",
         target: "es2020",
         sourcemap: "linked",
+        sourceRoot: "..",
         loader: {
           ".node": "copy",
         },