Update Migration documentation to include updated open-graph property names

[mim289]

The only migration documentation I could find for going from v1.x to v2.x was within the release notes themselves. The primary breaking change I found documented including the new open-graph.json component, but the property names cause a collision with TS compiling alongside GraphQL. I know the root issue has been resolved by swapping og:title to ogTitle, etc., but there is no outward-facing documentation to point users to this new property naming schema. I only found it as I was digging through open issues and down into pull requests.

Obviously not a breaking or major change request, just a helpful little thing for devs like me migrating from Strapi v4 to v5! Thanks so much for the plugin and your continued efforts!