style: add editorconfig file

tests/short_sha.bats

@@ -16,4 +16,4 @@ test_short_sha(){
   actual="$(short_sha ${given})"
   echo "expected : [${expected}], actual : [${actual}]"
   [ "${actual}" == "${expected}" ]
-}
+}

tests/slug_ref.bats

@@ -52,4 +52,4 @@ test_sluf_ref() {
   actual="$(slug_ref \"${given}\")"
   echo "expected : [${expected}], actual : [${actual}]"
   [ "${actual}" == "${expected}" ]
-}
+}