Add SocialWick as bronze sponsor

[wing328]

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Summary by cubic

Add SocialWick as a bronze sponsor across the site to display their logo and link.
Updates sponsors.yml and the README sponsor grid, and adds img/companies/socialwick.png with a UTM-tracked link to socialwick.com.

^{Written for commit 1ddcdc7. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 3 files