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/makeBuffer.ts

@@ -0,0 +1,8 @@
+export function makeBuffer(bytes: number[]): ArrayBuffer {
+  const buffer = new ArrayBuffer(bytes.length);
+  const dv = new DataView(buffer);
+  for (let offset = 0; offset < bytes.length; offset++) {
+    dv.setUint8(offset, bytes[offset]);
+  }
+  return buffer;
+}