Add image metadata to blog posts

Description

This PR adds image metadata to blog posts so that custom images appear when sharing on social media.

[!NOTE]

I can't test if the custom images actually appear as social cards since the updated pages that include the image metadata need to be live.

N/A

[x] I have updated the side navigation as necessary. N/A
[x] I have updated the documentation to reflect the changes. N/A
[x] I have documented or updated any remaining open issues linked to this PR in GitHub, Obsidian, etc. N/A

[x] I have merged and published any dependent changes in other PRs. N/A
[x] I have commented my code, particularly in hard-to-understand areas. N/A
[x] I have checked that my changes look as expected on a locally built version of the docs site.
[x] My changes generate no new warnings.