Add StructuredCloneable type

[thecodewarrior]

This adds two types for values losslessly cloneable using structuredClone.

Notes:

• The web and non-web types are separate so people who aren't writing browser code don't pull in web types
• Custom error classes do match, despite the fact that structuredClone isn't able to losslessly clone them (they're cloned as base Error instances). After doing some research I couldn't figure out a way to include the root Error class but exclude subclasses, so I just accepted the limitation and documented the discrepancy.

Fixes #855

[Emiyaaaaa]

I think this PR needs to wait for #898 to merge.

[sindresorhus]

Tests are failing now. Not sure how we can handle DOM types conditionally.

[thecodewarrior]

I'm not sure there's a way to conditionally enable dom types. I tried using a triple-slash directive but that seems to include the DOM types across the entire project.

Though if we aren't including DOM types in type-fest in general, we could just remove the web variant. The only DOM types I can really foresee having widespread use would be Blob and File, both of which seem to compile successfully without the DOM library, so they can just be folded into the standard variant.

[sindresorhus]

Relevant: microsoft/TypeScript#31894

[sindresorhus]

I think we could do it by adding a dom sub-export in package.json: https://nodejs.org/api/packages.html#subpath-exports

[thecodewarrior]

Adding the sub-export would probably involve changes to the testing/build infrastructure (running twice for non-dom/dom builds), which I'm not familiar with, but if you want to implement that I'd be happy to add back the web type. If we're doing a sub-export I think it wouldn't even need to have a separate name, just import {StructuredCloneable} from 'type-fest/dom' instead of import {StructuredCloneable} from 'type-fest'

[sindresorhus]

Thanks :)