scikit-learn GitHub dashboard: update with Sponsors button and more

[reshamas]

Updates to add

• add Sponsors button (https://docs.github.com/en/sponsors/receiving-sponsorships-through-github-sponsors/setting-up-github-sponsors-for-your-organization)
• add in social media links for most widely used channels: LinkedIn, YouTube, Blog
• no public email addresses, to avoid spam
• need to create a .github repo for org level links for sponsorship

Notes

• this issue is best for a maintainer because they have org-level access to create repo's and make admin updates

Example 1: of Data Umbrella

• https://github.com/data-umbrella

Example 2: scikit-learn

https://github.com/scikit-learn

Example 3: .github repo's of other orgs

• Data Umbrella: https://github.com/data-umbrella/.github
• PyMC: https://github.com/pymc-devs/.github

[adrinjalali]

Thanks @reshamas , I've submitted our org's sponsor page proposal now to GitHub, awaiting approval.

I also created the scikit-learn/.github repo and added the comms and docs teams as maintainers there. So I think the permissions are now set and ready for you to set them as you see fit :)