[typescript-language-features] Expandable hover

[gabritto]

TypeScript counterpart: microsoft/TypeScript#59940

See description of the TS PR for what's currently supported.

[mjbvz]

@gabritto Should we merge this for testing? If you prefer we can gate this behind an experimental setting too

[gabritto]

@gabritto Should we merge this for testing? If you prefer we can gate this behind an experimental setting too

As discussed offline, I'll implement the missing part of detecting when expansion is possible or not (both in this PR and on the TSServer PR), and then we can merge this for testing.

@mjbvz can you point me to how to add a vscode setting to gate this?

[mjbvz]

Thanks @gabritto. For the setting, try taking a look at typescript.autoClosingTags. If the new setting is called typescript.experimental.expandableHover, you can use something like this to check it at turn time:

vscode.workspace.getConfiguration('typescript').get('experimental.expandableHover');