NumFOCUS -> LF Charities changes

[jasongrout]

These changes update our website to reflect our new home at LF Charities.

[jasongrout]

@Carreau - it seems the netlify handler is having issues: https://app.netlify.com/sites/jupyter-github-io/deploys/671193d6a2b3c700089590c0

Is that handler under your account? It says "Matthias Bussonnier's team/jupyter-github-io"

[jasongrout]

Our netlify preview seems to have problems right now, but here is the donate box at the bottom of jupyter.org/about after this PR:

[Carreau]

Hum here is the error,

An error occurred while installing bigdecimal (3.1.8), and Bundler cannot
continue.

In Gemfile:
  github-pages was resolved to 232, which depends on
    jekyll-mentions was resolved to 1.6.0, which depends on
      html-pipeline was resolved to 2.14.3, which depends on
        activesupport was resolved to 7.2.1.1, which depends on
          bigdecimal
Error during gem install

Let me know if you need someone to be added to the team, but I think on free plan I'm already at the limit.

[Carreau]

Well I tried a random change and it appear that worked...

Anyway, I don't think nettlify really support ruby officially, so maybe we should move to a github action, IDK.

[fperez]

I approve the content changes of the PR. I see some failures still in CI, though the PR addresses already a few issues.

As long as those failures can be ignored for the site to build, I say 🚀 . Thanks @jasongrout !

[jasongrout]

I just reran the failing checks and they passed. I think we are good on that front.