Add the Digital Public Good (DPG) badge

[Xpirix]

Feature Description

From @timlinux and @mbernasocchi

QGIS has been approved as a digital public good (DPG).

We should write an approach and showcase this achievement on the QGIS Website.

Reference to Feature

No response

[Xpirix]

@timlinux

I think we can use the DPG badge as described here: DPGAlliance/dpg-community#36

For the website, please find below some suggestions:

• Display the badge on the Homepage and the README of the repository.
• (Optional) Create a new page that showcases the details of the badge. We can also share the link to this page when posting the announcement.
• Link the badges to the new page or directly to the DPG Registry