Compile all markdown files in current directory if no arguments are given

If no arguments were given, instead of showing the help, search for all markdown (*.md, *.markdown, *.mdown, *.md.txt) files in the directory the command was invoked from, and compile each of them.

Maybe show a confirmation dialog if there are more than 10 files.

[simonhaenisch]

@karlhorky if all files are in the same directory, you can even just do md-to-pdf dir 🤓 I’m actually planning to allow shell globbing so you can pass in a list of files, however it’s going to be a breaking change and I want to do a few other things along with it.

[karlhorky]

As mentioned in #22, a workaround for this with the current version is a shell for loop:

{
  "scripts: {
    "build": "for file in dir/*.md; do md-to-pdf $file; done"
  }
}

Ref: https://github.com/karlhorky/npm-scripts-tricks/blob/master/readme.md#run-a-command-for-all-files-in-a-directory