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/DuckDBValue.ts

@@ -0,0 +1,9 @@
+import { SpecialDuckDBValue } from './SpecialDuckDBValue.js';
+
+export type DuckDBValue =
+  | null
+  | boolean
+  | number
+  | string
+  | bigint // TODO: Should types requiring bigint be SpecialDBValues?
+  | SpecialDuckDBValue;