Add alias for scala

Currently, there isn't a defined alias for scala. I propose adding `sc` as that alias.

Even better would be if there was a ability to define your own aliases in preferences (like Dash).

Start by locating how documentation aliases are defined and resolved, then trace the entry point used when selecting Scala documentation. Make the `sc` alias resolve to Scala and verify the existing alias behavior; custom aliases in preferences are a separate, broader proposal whose scope is not defined here.

Written by the indexing model from the issue text.