New functionality
* Improve assemble scalar and add norm compilation by jorgensd in https://github.com/scientificcomputing/scifem/pull/100
* Add convenience function to find 'exterior' facets of a subdomain and finding interface by jorgensd in https://github.com/scientificcomputing/scifem/pull/101
**Full Changelog**: https://github.com/scientificcomputing/scifem/compare/v0.4.0...v0.5.0