make: explain why the target "bin/release-version" exists
make: explain why the target "bin/release-version" exists

Signed-off-by: Maël Valais <d58a90d9f168821bded9222e523244d2fab951f8@vls.dev>

jetstack/cert-manager,cert-manager/cert-manager,jetstack/cert-manager,cert-manager/cert-manager,cert-manager/cert-manager,jetstack/cert-manager