README: de-jargon feature list, fixup (#428)

* README: de-jargon feature list, fixup

Signed-off-by: William Woodruff <william@trailofbits.com>

* Update README.md

Co-authored-by: Dustin Ingram <di@users.noreply.github.com>
Signed-off-by: William Woodruff <william@yossarian.net>

Signed-off-by: William Woodruff <william@trailofbits.com>
Signed-off-by: William Woodruff <william@yossarian.net>
Co-authored-by: Dustin Ingram <di@users.noreply.github.com>

README.md

@@ -39,9 +39,10 @@ else!
 
 ## Features
 
-* Support for signing Python package distributions using an OpenID Connect identity
-* Support for publishing signatures to a [Rekor](https://github.com/sigstore/rekor) instance
-* Support for verifying signatures on Python package distributions
+* Support for keyless signature generation and verification with [Sigstore](https://www.sigstore.dev/)
+* Support for signing with ["ambient" OpenID Connect identities](https://github.com/sigstore/sigstore-python#signing-with-ambient-credentials)
+* A comprehensive [CLI](https://github.com/sigstore/sigstore-python#usage) and corresponding
+  [importable Python API](https://sigstore.github.io/sigstore-python)
 
 ## Installation