Support hsc files in autodetect

[googleson78]

We should also autodetect hsc files. This however depends on rules_haskell supporting hsc files in haskell_module rules, which it currently doesn't.

[googleson78]

PR opened for haskell_module hsc support: tweag/rules_haskell#1731

[googleson78]

This is done on the rules_haskell side, so it should be safe to do this now.

Actually I guess we should wait for a release from rules_haskell?