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-reader/src/DuckDBRow.ts

@@ -0,0 +1,5 @@
+import { DuckDBValue } from '@duckdb/data-values';
+
+export interface DuckDBRow {
+  readonly [columnName: string]: DuckDBValue;
+}