Fix Vs code extension

[hschne]

This fixes #1864. Root cause is the upgrade from vscode-languageserver 9.0.1 to 10.0.0.

Version 9 exposed its Node.js entry point as a regular file, but Version 10 changed the package to use conditional exports. Its Node.js entry point is now declared roughly like this:

{
  "exports": {
    "./node": {
      "types": "./lib/node/main.d.ts",
      "node": "./lib/node/main.js"
    }
  }
}

Rollup's node-resolve plugin does not enable that conditional node export by default. The fix is simply to use nodeResolve's exportConditions.