Fix opengraph partial ld+json never activated

[barefootstache]

Pull Request type

Please check the type of change your PR introduces:

• Bug-fix
• Feature (functionality, design, translations, etc.)
• Documentation change
• Project management (tests, CI, GitHub configuration, etc.)
• Other (please describe):

Current state

Closes #475

Proposed changes

• add missing setting blogDir missing in the exampleSite/config/_default/params.toml which is referenced in layouts/partials/opengraph.html
• extend opengraph partial with a more complete keywords, tags, and categories references both within the ld+json script and outside of it

Screenshots, if applicable

Checklist

• Bug-fixes and new features: I have tested locally with the latest release of Hugo extended. This requirement is a standard.
• Bug-fixes, new features, and doc changes: I have updated the relevant documentation as part of this PR.
• All PRs: I have signed off (using git commit -s ...), or if not possible due to developer environment constraints, will comment below confirming that I am adhering to the Developer Certificate of Origin.

[barefootstache]

@chipzoller fixed the broken Github actions by merging PR #478 into the branch.

[chipzoller]

Thanks, was hoping to merge that one first.

[chipzoller]

Thank you for this fix. @onweru, can you help test and confirm safe?