[DOCS]: undocumented removed TS types `PgDatabase` and `PgTransaction` in v1 release candidate

### Enhancement hasn't been filed before.

- [x] I have verified this enhancement I'm about to request hasn't been suggested before.

### Describe the enhancement you want to request

I'm using the `PgDatabase` and `PgTransaction` types to expose `$client` via declaration merging, but these types are no longer exported from the v1 release candidate:

```ts
import {
NodePgDatabase,
type NodePgQueryResultHKT,
} from "drizzle-orm/node-postgres";
import * as schema from "./schema.ts";
import type { Pool } from "pg";
import type { PgDatabase, PgTransaction } from "drizzle-orm/pg-core";
import type { ExtractTablesWithRelations } from "drizzle-orm";

declare module "drizzle-orm/node-postgres/driver" {
export interface NodePgDatabase<
TSchema extends Record = Record,
> extends PgDatabase {
// declaration merge this into the class type
$client: Pool;
}
}

export type Database = NodePgDatabase;
export type Transaction = PgTransaction<
NodePgQueryResultHKT,
typeof schema,
ExtractTablesWithRelations
>;
```

Review the v1 release-candidate entry points shown in the example: drizzle-orm/node-postgres, drizzle-orm/pg-core, and drizzle-orm/node-postgres/driver. Check how PgDatabase and PgTransaction are currently exposed or replaced, then update the relevant documentation to explain their availability and declaration-merging usage. Done means users can determine the supported types and imports from the documentation.

Written by the indexing model from the issue text.