Enforce root-relative URL syntax and open links in new tabs

[httphypixelnet]

Description

Added

• rehype-external-links.ts: Rehype plugin to ensure external links open in a new tab
• remark-force-root-relative.mjs: Remark plugin to enforce root-relative URLs on internal links

Closes #37

Meta

Merge checklist:

• Pull Request title is short, imperative summary of proposed changes
• The description documents the what and why, including events that led to this PR
• Pull Request has been linted and formatted and follows the styleguide

[github-actions]

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[samfreund]

I believe absolute links is covered by af64f50

I misinterpreted the purpose of the absolute links

[httphypixelnet]

I believe absolute links is covered by af64f50

The current lint/build tooling doesn't fail on src/content/docs/learning-course/stage1/stage1b/stage-overview.mdx so I'm going to assume it does not cover absolute links.

[samfreund]

I believe absolute links is covered by af64f50

The current lint/build tooling doesn't fail on src/content/docs/learning-course/stage1/stage1b/stage-overview.mdx so I'm going to assume it does not cover absolute links.

It does, I think the reason that doesn't work is because src/content/etc. is the root path. Haven't tested with that combination though, so can't confirm. Regardless, it doesn't cover some of the https links you're changing so that's a good fix.

[httphypixelnet]

Strange, you want me to investigate making the plugin work properly?