Fix #2101 support externalSymbolLinkMappings wildcard

[mistic100]

This solves #2101 with the syntax suggested in said issue.

{
    "externalSymbolLinkMappings": {
        "external-lib": {
            "SomeObject": "https://external-lib.site/docs/SomeObject",
            "*": "https://external-lib.site/docs"
        }
    }
}

[mistic100]

A question I have is should we bring this further ? Like regex match ? or URL templating ?

{
  "*": "https://external-lib.site/docs/${name}"
}

I feel it will never cover all possible cases (In my case three.js documentation URL is categorized so only an full explicit configuration can work if I want complete links). So perhaps just keep it simple.

[Gerrit0]

I think simple is good, at least initially. Maybe glob matching in the future, but I don't really see a use case for it that wouldn't be better served by writing a plugin. This option is really meant for one offs, for bigger things (linking to MDN, Node docs) a plugin is much more scalable.

[Gerrit0]

This is perfect, thank you!