Improve look of Donors list in Editor's About

[Mickeon]

This PR does a few things to improve how Donors are visualized in the Editor's About section:

• Website links are hidden within the donor's name.
  • Donors with associated websites display an icon.
  • Hovering over these donors displays their website if it exists.
  • Double-clicking opens the website on browser.
• The "And _ anonymous donors" part is grayed out.
• Most donors are always split in 3 equally-spaced columns regardless of size.
• Internally, get_logo was removed. It went entirely unused.

Note that the Authors page is not (currently) affected.

[Mickeon]

Should be all good now. I gave up trying to lazy-load the About section on NOTIFICATION_READY. It would just crash and the debugger was not helpful in troubleshooting it.

[KoBeWi]

When you click an item, it loses its hover highlight:

godot.windows.editor.dev.x86_64_ezdfAHByTE.mp4

[Mickeon]

Yyyyeah, I thought that the default harsh highlight was a tad excessive so I used an empty StyleBox for it. Either I revert it, or I change the style to use the more "normal" highlighting used when there is a selection but no focus.
I think selected_focus is the culprit?

[KoBeWi]

Overall looks ok.

[Mickeon]

Updated the PR to use font_disabled_color instead of hardcoded Color(1, 1, 1, 0.5) for the ExternalLink icons.

[akien-mga]

Thanks!