New feature: Glob support as alternative to directory path

[paul-hammant]

npx mddb "**/*.md" would be nice.

I'm in a Git checkout and would want to recurse all markdown from root (not a blog with a _blog/ path). I want it to ignroe the .git/ folder and while there's no --ignore-paths feature or default ignores, and inclusing glob would help.

Without it, I might have to do some find -exec fu.