Add fixer for return-never-call

[ajafff]

Implement an autofixer for return-never-call (#159).

It should only add throw or return if there are no executable statements after the failing statement. That's necessary to avoid breaking people's build by making code unreachable. To be fair the code is already unreachable but not detected by the compiler.

This needs some control flow analysis to track if any statement is executed after the current one.

[ajafff]

instead of providing an autofix that requires a control flow graph, this rule could provide a CodeAction (#316) to fix this issue.