docs(guide/migration): fix link to #2500
docs(guide/migration): fix up internal links
chore(release): update version number for next round of development
chore(package.json): revert to marked@0.2.9 to fix CI builds

The marked npm library brought in a breaking change at 0.2.10.
This commit ensures that we get exactly the version we want.

Closes #4822
docs(guide/migration): fix internal link