[Feature request] Make helper functions of format/base.go public to be able to easily extend format.Format

[bastantoine]

Hello!

I've just discovered your tool, it's awesome and really useful!

I'm using your tool for a work project, but I need to tweak a bit the rendered markdown files. I saw that there are bunch of markdown helpers (bold, header, link...) in format/base.go that you use in all the implementation of format.Format (PlainMarkdown, GitHubFlavoredMarkdown and AzureDevOpsMarkdown).

I was wondering if it would be possible to export those helpers so that its easy to create a custom implementation of format.Format, without having to rewrite those helpers?

I'd be happy to send a PR if that's okay with you!

[bastantoine]

Hello @princjef ! Any news on this?

[princjef]

Hey @bastantoine, that sounds like a great idea! If you want to put together a PR with the changes I'll take a look and we can get it merged

[bastantoine]

Great, thanks!