feat(docs): add tip about expired ghcr.io creds (#778)

Signed-off-by: Nicholas Morey <[email protected]>
Co-authored-by: Kent Rancourt <[email protected]>

docs/docs/20-quickstart.mdx

@@ -139,6 +139,26 @@ The Kargo dashboard will be accessible at
 
 The Admin password is `admin`.
 
+:::tip
+```
+Error: INSTALLATION FAILED: failed to authorize: failed to fetch oauth token: unexpected status: 403 Forbidden
+```
+
+If you recieve this error, it's likely because `docker` is configured to
+authenticate with `ghcr.io` using an expired token.
+
+You can confirm this by running:
+```
+docker pull ghcr.io/akuity/kargo:v0.1.0-rc.21
+```
+```
+Error response from daemon: Head "https://ghcr.io/v2/akuity/kargo/manifests/v0.1.0-rc.21": denied: denied
+```
+
+To solve this problem, either remove the invalid credentials for `ghcr.io` by
+running `docker logout ghcr.io` or re-authenticate by running `docker login ghcr.io`
+:::
+
 ## Trying It Out
 
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