git: openjdk/jdk-sandbox: classfile-api-branch: readme update

[Adam Sotona]

Changeset: 928fa75a
Author:    Adam Sotona <asotona at openjdk.org>
Date:      2023-04-11 09:59:38 +0000
URL:       https://git.openjdk.org/jdk-sandbox/commit/928fa75a63701684c8381f6006201f615aba7824

readme update

! README.md