v0.4.2

fix(build): vendor openssl for git2 to fix macOS x86_64 cross-compile

git2's default features include https, which pulls in openssl-sys.
On macos-latest (aarch64) cross-compiling to x86_64, pkg-config can't
locate openssl for the target triple, causing the release build to fail.

Adding 'vendored-openssl' bundles openssl with libgit2, removing the
system dependency and making the cross-compile deterministic.

Refs: v0.4.2 release build failure on x86_64-apple-darwin