New CompletionItemTag for completions that import a new dependency

Hi everyone,

We are currently designing on our VSCode fork a way of showing on the client if a dependency is going to be auto-imported/added when a completion item is added.

From a UX standpoint, this is important for us since we have a big monorepo and adding a new dependency might make the building times slower as well as raising other issues and quirks. For that reason, we want to nudge users that selecting an specific item is going to import a dependency via the additionalTextEdits.

Since this might be useful not only for us, I am suggesting we add a new CompletionItemTag value named: ImportsDependency, AddsDependency or any other similar wording.

This would make it available for clients to show such a hint in case completions coming from language servers are also going to auto-import a dependency.

What are your thoughts regarding that?
I am happy to help with a PR, if you think that is useful.

The issue names no files, tests, or entry points. Review the existing CompletionItemTag and additionalTextEdits protocol definitions, then determine the tag wording, semantics, and client-facing behavior needed to signal that a completion adds a dependency.