* feat(v2): add ability to set custom heading id
* Add cli command
* Fix slugger
* write-heading-ids doc + add in commands/templates
* refactor + add tests for writeHeadingIds
* polish writeHeadingIds
* polish writeHeadingIds
* remove i18n goals todo section as the remaining items are quite abstract/useless
* fix edge case with 2 md links in heading
* extract parseMarkdownHeadingId helper function
* refactor using the shared parseMarkdownHeadingId utility fn
* change logic of edge case
* Handle edge case
* Document explicit ids feature
Co-authored-by: slorber <lorber.sebastien@gmail.com>