"header" aliases have been removed in markdown-cli2

[chadfawcett]

We recently updated markdownlint-cli2 on The Hub and noticed we started receiving increased errors related to headings. I dove into why and noticed that markdownlint-cli2 has removed the rule aliases that use the word "header" in favour of "heading".

As per the commit message, "header" aliases were deprecated in v0.9.0. I checked your package.json and saw you're depending in v0.13.0 but still have rules with the "header" alias.

These rules should be updated to use "heading" instead of "header".

[khiga8]

Hey @chadfawcett! Thank you for your contribution and fixing this!

I've just cut a new release - https://github.com/github/markdownlint-github/releases/tag/v0.6.3!