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-data-values/src/DuckDBStructEntry.ts

@@ -0,0 +1,6 @@
+import { DuckDBValue } from './DuckDBValue.js';
+
+export interface DuckDBStructEntry {
+  readonly key: string;
+  readonly value: DuckDBValue;
+}