fix(docs): update Astro Docs links to match v6 branch

[ArmandPhilippot]

Changes

Updates a few links to Astro Docs v6 to match the new structure:

• a heading has been renamed (#set becomes #sessionset, I also added the v6 subdomain because this change does not exist in docs main website)
• some links related to CSP were broken but not caught in our CI because of the v6 subdomain
• two changesets have been updated... we don't have a TODO link in docs 😄 (related to feat: loader.createSchema() #14759 if you want to check this is correct)

Testing

N/A (well, I checked the links manually)

Docs

Changeset, and because this is a docs update:
/cc @withastro/maintainers-docs for feedback!

[changeset-bot]

🦋 Changeset detected

Latest commit: 4ddff0d

The changes in this PR will be included in the next version bump.

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[codspeed-hq]

Merging this PR will not alter performance

✅ 18 untouched benchmarks

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_{Comparing armand/fix-docs-links (4ddff0d) with main (67f9f96)}

[delucis]

I tested all the links and they all took me to the right place!

I haven’t been following this aspect, but is the intention to update all these v6.docs.astro.build URLs to point to the main docs before v6 is stable?

[ArmandPhilippot]

Thanks!

I think that's the plan, yes. We can't do that now because this would result in broken links in the JSDocs (and some errors I believe). I don't have a date for swapping the links but I know Florian has created a project card to track this!

[sarah11918]

Thank you!