feat: add Makefile
feat: add Makefile

This streamlines and simplifies local development by adding
a Makefile based on the commands in the README.md

sbarzowski/go-jsonnet,google/go-jsonnet,sbarzowski/go-jsonnet,sbarzowski/go-jsonnet,sbarzowski/go-jsonnet,sbarzowski/go-jsonnet,google/go-jsonnet,google/go-jsonnet,google/go-jsonnet,google/go-jsonnet