add duckdb-ui-client & other ts pkgs (#10)

* add duckdb-ui-client & other ts pkgs

* workflow fixes

* fix working dir

* no sparse checkout; specify package.json path

* path to pnpm-lock.yaml

* add check & build test

* workflow step descriptions

* use comments & names

* one more naming tweak

ts/pkgs/duckdb-ui-client/test/helpers/mockRequests.ts

@@ -0,0 +1,15 @@
+import { RequestHandler } from 'msw';
+import { setupServer } from 'msw/node';
+
+export async function mockRequests(
+  handlers: RequestHandler[],
+  func: () => Promise<void>,
+) {
+  const server = setupServer(...handlers);
+  try {
+    server.listen();
+    await func();
+  } finally {
+    server.close();
+  }
+}