Add import statement to ref pages

Every ref page about runtime symbols should have

```ts
import { x } from "y";
```

at the top, with three tabs (TS/JS/Deno) as always.

Every ref page about types should have

```ts
import { type x } from "y";
```

at the top, with two tabs (TS/Deno).

Start by locating the reference pages for runtime symbols and types, then inspect how the existing TS/JS/Deno tabs are defined. Add the appropriate import example to each page, preserving three tabs for runtime symbols and two for types. Done means all relevant ref pages show the requested import at the top with the correct tabs.

Written by the indexing model from the issue text.