Move documentation linting to its own repository

[GuySartorelli]

We're pulling linkfield docs in from that repository, and aim to pull more in going forward:

• Pull documentation through into docs.silverstripe.org silverstripe-elemental#985
• Pull documentation through into docs.silverstripe.org silverstripe-userforms#1266
• Pull documentation through into docs.silverstripe.org silverstripe-mfa#531

We should pull the documentation linting stuff into its own repository that can be shared across all relevant repos.

Acceptance criteria

• Linting configuration (i.e. declaring what linting rules are applied) is in the new repository
• All dependencies (npm and composer) are handled in the new repository
• Repositories with documentation don't need any configuration beyond indicating where their documentation lives
• Documentation can be linted using a command that gets added to vendor/bin/
• Documentation can be linted both when the repository with documentation is the root dir (i.e. CI) and when it is in vendor (i.e. locally)
• developer docs itself has the new linting repo as a dev dependency
• Other repositories with documentation list the new repository as a composer dev dependency
• All repositories currently pulling documentation into the developer docs site have the new linting applied
• Docs linting is added as a regular part of CI for all relevant repositories
• All cards for pulling new documentation in from additional repositories are updated so that adding linting is in the ACs
• New repo is in packagist
• New repo has appropriate branch protection rule
• New repo is added to zenhub board
• New repo is added to module standardiser
• New repo is added to rhino
• New repo is added to elvis

Note

• We'll exclude userhelp linting for now, but we'll create a follow card for applying linting to userhelp

PRs

CI showing developer-docs happy: https://github.com/silverstripe/developer-docs/actions/runs/8532499473?pr=489
CI showing the changes to the gha-* repos work as expected: https://github.com/GuySartorelli/silverstripe-linkfield/actions/runs/8545963893/job/23415708351

• NEW Migrate documentation linting to a new repository documentation-lint#1
• MNT Add documentation-lint repo rhino#18
• MNT Add documentation linting repo github-issue-search-client#135
• MNT Add documentation lint repo module-standardiser#41
• MNT Move linting to a dedicated repository developer-docs#489
• NEW Add documentation linting option gha-ci#112
• NEW Add docuemntation linting matrix entry gha-generate-matrix#84
• NEW Add docs linting step gha-run-tests#23
  Do not merge anything below this line until the CI PRs have been merged and has been rerun on the below PRs.
• MNT Add documentation linting silverstripe-linkfield#271

After everything is merged, reassign to Guy so they can add to packagist and run standardiser across the new repo.

[GuySartorelli]

New repo is at https://github.com/silverstripe/documentation-lint

[emteknetnz]

Assigning back to @GuySartorelli so sort out packagist and ensure things are working as expected. You'll no doubt want to rerun builds for linkfield and developer docs

[GuySartorelli]

Turns out I don't have access to the machine user we use to add packages to packagist. Can you please do that step and then reassign to me?

[GuySartorelli]

new doc linting CI passing in both linkfield and dev docs