Fix loading of the LSP worker script in the online editor

The update to vite 4 triggered the vite 3 bug vitejs/vite#9879
for us, where the wasm-pack generated .js is included as iife and
therefore the use of import.meta.url gets transpiled to some shim that
tries to access the document, assuming that the JS is running in the
browser instead of in a worker environment.

Explicitly set the output type for the worker to ES modules, so that no
changes are needed and import.meta.url remains in use. This matches the
worker invocation anyway, as we pass "type": "module" to the Worker
constructor.

tools/online_editor/vite.config.js

@@ -21,6 +21,9 @@ export default defineConfig(({ command, _mode }) => {
             // We need to enable support for bigint
             target: "safari14",
         },
+        worker: {
+            format: "es",
+        },
     };
 
     let global_aliases = {