Goto definition on dbt variables

[jaredchurch]

I'm just starting with this extension and loving it as it makes my work with dbt-core and VS code so much better integrated!

One thing that would be a great extension to it would be being able to see values for dbt vars when I mouse over them, similar to the goto definitions for macros, models etc.

For example we have a variable referenced as: {{ var('cUnknownKeyValue') }} and it'd be great to be able to mouse over and see what actual value this expands too.