Widgets are falsely marked as not referenced

[Desteel]

Resolves 78

tsconfck only handles the first level of referenced (and perhaps it won't be changed).

Anyway, it is already enough to cover general cases, like:

• vite tsconfig's referenced;
• monorepo, assuming that the steiger is run for a specific subproject;
• monorepo, assuming that only the first level of referenced is used (which is expected)

In the future, if the tsconfck behavior is changed, it will be used by default.

[illright]

Great PR, I just don't think we should make this functionality exclusive to the FSD plugin of Steiger :D How about we make these changes in @feature-sliced/filesystem instead?

[illright]

Actually, I changed my mind, this function doesn't belong in the @feature-sliced/filesystem package. It doesn't belong to the FSD plugin either, but a better way to implement it needs some more thinking, so it will probably land in the next release of Steiger (see #107).

Thanks for this PR! Sorry it took so long :D