new_variant: update links in documentation

The document "Working with coreboot Upstream and Chromium" moved from
drive to the Chromium docs, so update the link. Add a link to the
Wyvern tutorial video.

BUG=None
TEST=N/A

Change-Id: If5e1e6208d0b8ae3117f2795e2b7fd9faa3c877f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2321301
Tested-by: Paul Fagerburg <pfagerburg@chromium.org>
Auto-Submit: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
diff --git a/contrib/variant/README.md b/contrib/variant/README.md
index 4876f8a..2ed6347 100644
--- a/contrib/variant/README.md
+++ b/contrib/variant/README.md
@@ -791,6 +791,9 @@
 
 ### Uploaded CLs for "Wyvern" variant
 
+A screen capture video of the process to create Wyvern is available:
+[Wyvern_tutorial_with_subtitles](https://drive.google.com/file/d/1t-JWTSfCyvL-oHmykyi1i5rdSYAyANmm/view?usp=sharing)
+
 The following CLs were created and uplodaded by `new_variant.py`:
 * [42551](https://review.coreboot.org/c/coreboot/+/42551) hatch: Create wyvern
 variant
@@ -826,6 +829,6 @@
 
 # References
 
-* [Working with coreboot Upstream and Chromium](https://docs.google.com/document/d/14IBkP2Mk-2FtI26VINQRCuMA-vyhuRdSpHHaTfujS9Q/)
+* [Working with coreboot Upstream and Chromium](https://chromium.googlesource.com/chromiumos/docs/+/refs/heads/master/firmware/coreboot_upstream.md)
 * [How To: Building coreboot-upstream within Chromium OS](https://docs.google.com/document/d/1H7u99Pk0EGqcsROciFyoXIdpsL-AwcpfJG7VI2UDNFw/)
 * [ChromeOS Unibuild New Variant Design Doc](https://docs.google.com/document/d/1nAJblS29W4SMsGPPijfZED1QRYFMHeW2w_9ooPvEO_U)