Support globs for input files and map files

[ericcornelissen]

Improve the usability of the CLI by adding support for globs in the paths for input files and map files. This makes it a lot easier to cover a bunch of files in a single call, e.g.:

# instead of
$ wordrow -m ./map-1.md -m ./map-2.md ./input-1.txt ./input-2.txt

# just do
$ wordrow -m ./*.md ./*.txt