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/esm.mjs

@@ -0,0 +1,16 @@
+import commander from './index.js';
+
+// wrapper to provide named exports for ESM.
+export const {
+  program,
+  createCommand,
+  createArgument,
+  createOption,
+  CommanderError,
+  InvalidArgumentError,
+  InvalidOptionArgumentError, // deprecated old name
+  Command,
+  Argument,
+  Option,
+  Help
+} = commander;