Add Radiant Earth to fiscal host list (#58500)

Co-authored-by: mc <[email protected]>

Author: slincoln75

content/sponsors/receiving-sponsorships-through-github-sponsors/using-a-fiscal-host-to-receive-github-sponsors-payouts.md

@@ -24,6 +24,7 @@ When you sign up for a {% data variables.product.prodname_sponsors %} profile so
 * [Open Collective Europe](https://opencollective.com/europe)
 * [Open Source Collective](https://opencollective.com/opensource)
 * [Python Software Foundation](https://www.python.org/psf-landing/)
+* [Radiant Earth](https://radiant.earth/)
 * [Software in the Public Interest](https://www.spi-inc.org/)
 * [Software Underground](https://softwareunderground.org/)