feat: initial CLI structure

- init: create plugin boilerplate
- install: install from local path with deps
- list: show installed plugins
- validate: check manyplug.json syntax

node_modules/commander/typings/esm.d.mts

@@ -0,0 +1,3 @@
+// Just reexport the types from cjs
+// This is a bit indirect. There is not an index.js, but TypeScript will look for index.d.ts for types.
+export * from './index.js';