Refactor fetchSponsors to use consume GitHub Sponsors

[LeoColomb]

Closes #426
Fixes #427

[LeoColomb]

Ready to be reviewed.
Website preview: https://leo-gh-sponsors.yourls-website.pages.dev/
The commit highlighting how to add a featured sponsor: 5f50368
The rest of the commits covers GitHub Sponsors integration.

[ozh]

If I understand correctly, this fetches profile logo and link from their opencollective profile ?

If the sponsors provides a custom link or, as in latest case, a custom logo, how do we manage ?

[ozh]

(or if the sponsor just has no Opencoll profile and just a github account)

[ozh]

Proposal for a solution with flexibility (custom sponsor logo, URL, name) and automation (checking on opencoll if the sponsorship is still on)

We would have a angel-sponsors.md file with a simple table like so:

sponsorname	opencoll	github	URL	logo
Some Company	somecomp	somecomp		https://website/logo.png
Other Corp		other-corp	https://othercompany.co
Super Inc.		superinc
BairesDev	bairesdev	BairesDev-LLC	https://www.bairesdev.com/sponsoring-open-source-projects/	https://github.com/user-attachments/assets/caa67711-33df-4974-9bbe-cd2b7356712e

And the .js would check :

• if there is an opencoll or GH handle : check if sponsorship is on
• if there is an opencoll or GH : use fetched logo and URL from opencoll or Github, unless custom specified

[LeoColomb]

If the sponsors provides a custom link or, as in latest case, a custom logo, how do we manage ?

We don't, or I don't believe we should offer.

(or if the sponsor just has no Opencoll profile and just a github account)

As titled, this is the goal of this PR, to consume GitHub Sponsors sponsors and integrate their assets.
Have you checked the preview, by any chance?

And the .js would check :

• if there is an opencoll or GH handle : check if sponsorship is on
• if there is an opencoll or GH : use fetched logo and URL from opencoll or Github, unless custom specified

Yes, this is what is done by the script already.
The only difference is the logo, which is not currently customzable.
The "custom" URL is the website URL provided by their GitHub Sponsors profile or OpenCollective profile, something they can edit and most do.