Add a remark plugin to support custom header id

[dshevtsov]

Purpose of this pull request

This pull request (PR) adds a remark-heading-id plugin that allows validation of custom headers via remark-validate-links.

Test

See AdobeDocs/commerce-admin-developer#85

[jeff-matthews]

Approved for the basic functionality, but I want to note that this repo has special --ignore-patterns configured for the src/_includes and src/pages/graphql/schema directories.

For background, we originally added these patterns because of the false positives with custom header IDs. However, we've since expanded that to ignore frontmatter for the graphql schema directories. I assume we also need to ignore the _includes in the frontmatter checks as well.

Ideally, we would not ignore directories when testing.

[jeff-matthews]

But maybe the frontmatter config makes it unnecessary to use CLI ignore patterns: https://github.com/AdobeDocs/commerce-webapi/blob/main/.remarkrc.mjs#L17.

[keharper]

Coincidentally, in #246 I just deleted nearly 50 schema files that are no longer necessary now that the GraphQL schema docs link directly to SpectaQL. I don't know if it'll be possible to remove the pattern, but the remaining include files probably don't link to other include files.

[dshevtsov]

Approved for the basic functionality, but I want to note that this repo has special --ignore-patterns configured for the src/_includes and src/pages/graphql/schema directories.

For background, we originally added these patterns because of the false positives with custom header IDs. However, we've since expanded that to ignore frontmatter for the graphql schema directories. I assume we also need to ignore the _includes in the frontmatter checks as well.

Ideally, we would not ignore directories when testing.

@jeff-matthews please create a ticket for me to investigate the issue.

[jeff-matthews]

@dshevtsov, I created #247, which I think will eliminate the need for the --ignore-patterns option.