Psifr: Analysis and visualization of free recall data

This version adds support for analyzing prior-list intrusions. It also adds tools for working with semantic distance analyses. The documentation is expanded with examples for most functions.

• Marking of prior-list intrusions and analysis of the list lag of prior-list intrusions.
• Documentation of semantic distance analyses in the user guide.
• A utility for generating datasets from study and recall lists.
• Tools for working with semantic distance measures.
• Examples to illustrate most functions.
• Style reformatting using Black.
• A change to the automated testing system to use GitHub Actions.