Make it possible to customize the shortcode delimiters #12
Description
For example, instead of three braces for a block, use three colons; and for inline shortcodes square brackets might want to be used (in keeping with WordPress' precedent, which is where the name of this package comes from after all). Start and end delimiters should be separately configurable.
Some slightly related discussion here: https://talk.commonmark.org/t/github-is-beta-testing-their-own-admonition-syntax-we-should-weigh-in/4173