Provide detached signatures for bazelisk release binaries

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

Start by reviewing the Bazelisk release binaries and comparing them with the linked Bazel release assets and bazel-release.pub.gpg key. Done means each Bazelisk release binary has a matching detached .sig file generated with the release key and published alongside it.

Written by the indexing model from the issue text.