support the full python string format syntax

[geyang]

Hey David, First of all, thanks for this great library!

Particularly I'm interested in features like padding, number type formatting and date-time formatting. It would be interesting to have this work as a complete replica of the python string format function.

Some of the syntax can be found here: https://pyformat.info | Using format() for great good

[davidchambers]

Thanks for your feedback, @episodeyang. You'll be interested in #2. I worked on that pull request several years ago but didn't merge it because I didn't quite finish the test suite. Perhaps your interest will prompt me to spend time wrapping up the pull request, but I won't make any promises. ;)

You are welcome to use the mini-language branch, but an npm release would of course be preferable.

[zoswing]

Interested in #2，wonder when this version will be released