Fix logo in social card preview in Docusaurus

[josh-wong]

Description

This PR attempts to fix a bug with how the ScalarDB logo appears in the social card preview on social media sites like X and LinkedIn. The logo that appears in the social card preview is cut off, which is awkward.

Related issues and/or PRs

N/A

Changes made

• Added an image that has the same size that Docusaurus uses for their social card image.
• Changed the relative link for the social card to the newly added image.

Checklist

The following is a best-effort checklist. If any items in this checklist are not applicable to this PR or are dependent on other, unmerged PRs, please still mark the checkboxes after you have read and understood each item.

• I have updated the side navigation as necessary.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes.
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.).
• My changes generate no new warnings.
• Any dependent changes in other PRs have been merged and published.

Additional notes (optional)

N/A