Add option to disable diagnostics feature

[tk0miya]

Do you have a plan to disable the diagnostics feature (type-checking feature)? In other words, I'd like to enable the completion feature and the hover feature only.

On my project, the diagnostics are very noisy because my type definitions are very poor. It warns 400 or more violations even if I use steep with the lenient mode. Unfortunately, it hides other warnings and errors from other VSCode extensions. So I can't enable steep extension yet.

I know the goal of Steep is type-checking. But the option will become easy to start using types in Ruby projects. And it also will help to make Ruby developers familiar with types. I believe it will lead to empowering the typing culture in Ruby.

I'm not sure which steep-vscode or steep core is better to post this feature request. Please let me know if this is not a good place.

[tk0miya]

At present, the silent configuration has been introduced into the Steep (refs: soutaro/steep#800). So we no longer need to add a new option to the steep-vscode side. So closing this now. Thanks!