Add lefthook for linting and testing hooks, and optional pre-commit hook via local (#7)

* unbreak package lock

* lint

* add lefthook for prepush test and lint hook

* attempt at exiting 0 if we made a change in lint

* fix lint

* add fail text

* pre-commit test

* adjust autofix

* add lefthook example

* fix comment

lefthook-local.example.yml

@@ -0,0 +1,10 @@
+# Optional local lefthook configuration
+# To enable this:
+#  cp lefthook-local.example.yml lefthook-local.yml
+
+# Uncomment to add pre-commit hook for automatic linting on staged files:
+pre-commit:
+    commands:
+        lint:
+            run: npm run lint:fix {staged_files}
+            stage_fixed: true