Add an LSP / Autocompletion support

[abraithwaite]

Not sure what the best way to approach this problem is, but support for an LSP would be huge for obvious reasons.

Theoretically, this should be more straight forward than SQL because we have better context at the point of typing.

That is, context flows through the pipe, versus SQL SELECT a, b, c FROM X where we don't know the possible values for a, b, or c until the table X is specified.