chore: footer cleanup

[pReya]

I've reworked some minor things about the footer:

• Update all icons (clean up unnecessary markup in the SVG, resize all icons to be centered in their square 24px container, use currentColor)
• Inline icons (to be able to use currentColor)
• Update Twitter to X icon
• Fix noisy alignment of "internal-links" section (use a 3 col grid instead)
• Allow "newTab" and "relMe" props in toml
• Open all external links in new Tab
• Move ALL footer links to the toml file
• Move footer styles to their own _footer.scss file

Before:

After:

✔️ Checklist

• Check for common mistakes:
  • Wrap plain URLs in <> to linkify them (learn more).
  • Use the right level of headings: The page title will use a level 1 headings, so your headings should use level 2 and below.
  • Use internal links: when linking to another page on https://matrix.org, use the Zola [label](@/target.md) syntax.
• For blog posts:
  • Verify the date and post ordering on the /blog page, especially for multiple posts on the same day. Prefer UTC format, e.g. 2025-12-01T14:00:00Z for Dec 1st, 2025, 2pm UTC.
  • Set the correct author and category. Browse existing ones at https://matrix.org/author/ and https://matrix.org/category/ to match them.
• Let us know if you are contributing in a specific role, such as on behalf of an organisation or team, for example.
• Let us know if your PR is time-sensitive in any way.
• Mention any issues related to the PR. Use GitHub keywords as appropriate.
• Your individual commits or pull request is signed off.

[HarHarLinks]

lgtm, thank you!

we have historically not been doing an excellent job at tracking licenses for the icons, which is why they are missing in the existing files (see #2706, #2776). would you mind adding the license info for the new x.svg in https://reuse.software/ style?

[pReya]

would you mind adding the license info for the new x.svg in https://reuse.software/ style?

Big Companies typically grant a limited license to use their logos for purposes such as linking to a social media profile. However these are proprietary licenses, which are not part of any SPDX license list. So I'm afraid it's not possible/practical to do this for company logos such as Twitter, YouTube, etc.

The actual source for the logo was the official twitter brand site: https://about.x.com/en/who-we-are/brand-toolkit

[pReya]

@HarHarLinks Not sure if you saw my comment without tagging you.