Add .DS_Store to gitignore

See merge request !60

Replace remaining uses of 'cymake' with 'frontend'

See merge request !59

Add CI pipeline

See merge request !51

Make stack path configurable in Makefile

See merge request !52

Implement warning for shadowed imported names (-Wimport-name-shadowing)

Closes #133

See merge request !54

Improve frontend usability as a library

See merge request !58

Add support for implied language extensions (and let NoImplicitPrelude imply NoDataDeriving)

See merge request !57

Extract KnownTool type from Tool

See merge request !56

Add NoDataDeriving language extension

See merge request !55

This is more consistent with the way the other checks work, additionally
implied extensions are semantic information and should therefore not
be declared in a syntax module.