Promote "Metadata in Table Schema" recipe to the specs.

[pierrecamilleri]

Context and related issue : fix #899

Migrated pull request from datapackage-v2-draft repo

Still to do on this PR:

• [x] Move table schema to /standards/table-schema.md (cf. main)
• [X] Move changelog to /overview/changelog.md (cf. main)
• [x] Update wording so it aligns with Data Package (my pending PR)
• [x] Update some links
• [x] Fix invalid json example (it was an unintended change)
• [ ] Clarify if examples are borrowing title and path from Data Resource (I think they are, included in my PR) or if this is something completely separate.