Provide detached signatures for bazelisk release binaries

[wade-arista]

Would it be possible to sign the releases here like we do for bazel itself?

e.g. https://github.com/bazelbuild/bazel/releases/download/8.4.2/bazel-8.4.2-linux-x86_64 and https://github.com/bazelbuild/bazel/releases/download/8.4.2/bazel-8.4.2-linux-x86_64.sig which is generated using the bazel GPG key: https://bazel.build/bazel-release.pub.gpg

[fweikert]

Great idea! Unfortunately that would require us to migrate the release process to Buildkite, which probably won't happen anytime soon.