Doc: into type constructor: Make implicit import into explicit one

[windymelt]

The code examples in the documentation demonstrate the use of an into type constructor without explicit import statements. While the documentation's description of into's location implies the need for an import, I believe this documentation is incomplete. Therefore, I've added explicit documentation about the need for an import. The phrasing may still be improved.

Have you relied on LLM-based tools in this contribution?

No

[tanishiking]

As you mentioned, into is defined a few lines later in scala.Conversion. Asking for import Conversion.into above that definition feels a bit wired to me.
Also, it looks as if every later snippets requires the import, but some of them actually don't (like Example 1 call site).

What do you think about adding import Conversion.into in Example 2 instead? Then I think readers can infer import Conversion.into is required for every into usage as a type constructor.

[windymelt]

Thank you for response.

Yes, this approach seems appropriate.