Merge #20860: gitian-keys: add key for guggero

c3aa1a1 gitian-keys: add key for guggero (Oliver Gugger)

Pull request description:

  As asked in bitcoin-core/gitian.sigs#1427

  Full key(s) available at https://keybase.io/guggero/pgp_keys.asc

  ```
  -----BEGIN PGP SIGNED MESSAGE-----
  Hash: SHA512

  My key is F4FC70F07310028424EFC20A8E4256593F177720
  (Oliver Gugger <[email protected]>)
  -----BEGIN PGP SIGNATURE-----

  iQEzBAEBCgAdFiEEbgHuyWVpA7BUK48QA9tjIiZ8NzsFAl/0uXEACgkQA9tjIiZ8
  NzsMeQgAiuj0PqUQYRn3xyxdqAGpN/JdUgCC0HjolW44kDPvij1Tb1ZrvSQD1Amh
  H0XLca+eROGmdgSMNFIBcsh4/Ikh11hRVsbDtf2v2Q3xuM6abklzCFZto47QFgf6
  PZZIVUu9MespkOXOa8NK+nhsq241S6gp+dJkd39sW0q1+B7/7zVoV1v2tSCxkKeI
  x8TbHfH+BGhB0I7Kwanz/tz5rX5U7GdF8ajjKg4p/Z303UP6+j+j5eT4b8WJKVKN
  9N9mtx9h0sgo/i3Vk6KZ7Y74YYH3e3FL7ZVaoWxZgDPX79724F2l7K8n3q60F2X7
  jhB7uMTZ2trD7A2qtrpK7HnRVYlbVA==
  =AOM6
  -----END PGP SIGNATURE-----
  ```

ACKs for top commit:
  laanwj:
    ACK c3aa1a1

Tree-SHA512: 494b22bccb38b517fec642828d77e0ef50b07527d803be7374da1c54295e0e8958eee8a9ad0bbfbd47d4f553507011ac4417b02694a878ff4ce78639baa1801d

Author: laanwj

contrib/gitian-keys/keys.txt

@@ -26,6 +26,7 @@ CA03882CB1FC067B5D3ACFE4D300116E1C875A3D MeshCollider
 E777299FC265DD04793070EB944D35F9AC3DB76A Michael Ford
 9692B91BBF0E8D34DFD33B1882C5C009628ECF0C Michagogo
 77E72E69DA7EE0A148C06B21B34821D4944DE5F7 Nils Schneider
+F4FC70F07310028424EFC20A8E4256593F177720 Oliver Gugger
 D62A803E27E7F43486035ADBBCD04D8E9CCCAC2A Paul Rabahy
 37EC7D7B0A217CDB4B4E007E7FAB114267E4FA04 Peter Todd
 D762373D24904A3E42F33B08B9A408E71DAAC974 Pieter Wuille (Location: Leuven, Belgium)