ci: add cksum to benchmarks workflow

Add cksum to the CI benchmark matrix as requested in PR uutils#9064 feedback.

Author: naoNao89

.github/workflows/benchmarks.yml

@@ -24,6 +24,7 @@ jobs:
       matrix:
         benchmark-target:
           - { package: uu_base64 }
+          - { package: uu_cksum }
           - { package: uu_cp }
           - { package: uu_cut }
           - { package: uu_du }