README: re-add OIDC note

Signed-off-by: William Woodruff <[email protected]>

Author: woodruffw

Diff for: README.md

@@ -67,6 +67,11 @@ settings page of your project on GitHub. See [Creating & using secrets].
 
 ### Trusted publishing
 
+> **NOTE**: Trusted publishing is sometimes referred to by its
+> underlying technology -- OpenID Connect, or OIDC for short.
+> If you see references to "OIDC publishing" in the context of PyPI,
+> this is what they're referring to.
+
 This action supports PyPI's [trusted publishing]
 implementation, which allows authentication to PyPI without a manually
 configured API token or username/password combination. To perform