fix: replace broken Apex Ping sponsor with Open Collective

[Jerry-CodeHub]

Checklist

• I have ensured my pull request is not behind the main or master branch of the original repository.
• I have rebased all commits where necessary so that reviewing this pull request can be done without having to merge it first.
• I have written a commit message that passes commitlint linting.
• I have ensured that my code changes pass linting tests.
• I have ensured that my code changes pass unit tests.
• I have described my pull request and the reasons for code changes along with context if necessary.

Summary

• The Apex Ping links (apex.sh/ping) and associated image are no longer accessible
• Replaced with Koa's official Open Collective sponsorship page
• Added dynamic sponsor and backer badges from Open Collective

Changes

• Updated views/index.jade sponsor section
• Regenerated index.html

References

• Open Collective page: https://opencollective.com/koajs

Illustration