docs: add sponsor funding links

[kaanyagci]

Summary

• add a default GitHub Sponsors funding file for Makepad-fr repositories
• add a short sponsorship callout to the org profile README
• fix the existing Makepad-fr/vif.io profile link typo

Verification

• parsed .github/FUNDING.yml with Ruby YAML
• checked the commit is signed with the Makepad GPG key

Notes

• This PR only wires the repo/org-profile surfaces. GitHub Sponsors profile text and tier changes still need the Sponsors dashboard because the available API token cannot execute Sponsors tier/profile mutations.