bug: eslint rule cactbot-output-strings doesn't detect spread properties

[valarnin]

See commit f760614, which added an explicit unknown key to the const-defined output strings map, despite the key existing on the Directions.outputStringsCardinalDir constant.

[wexxlee]

Ref: More info on issue in prior repo: quisquous#5538

[MaikoTan]

I think it CAN be done by reading the ImportDeclaration statement, then programmatically invoking TypeScript's parser to get the AST of that file, and then following the properties to get all its keys. But this is really painful to do such a thing.
I am digging typescript declarations files, hoping this checking can be done by typescript itself rather than eslint.

[valarnin]

Even with the latest build of typescript, we can't force inference for this automatically, unfortunately.

It may make more sense to extract the ID of the trigger, then just import the triggerset directly and pull the computed outputStrings value from that, if we're dealing with it as a property (as opposed to cactbot-builtin-response setting it within the trigger).