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/fs-extra/lib/util/async.js

@@ -0,0 +1,29 @@
+'use strict'
+
+// https://github.com/jprichardson/node-fs-extra/issues/1056
+// Performing parallel operations on each item of an async iterator is
+// surprisingly hard; you need to have handlers in place to avoid getting an
+// UnhandledPromiseRejectionWarning.
+// NOTE: This function does not presently handle return values, only errors
+async function asyncIteratorConcurrentProcess (iterator, fn) {
+  const promises = []
+  for await (const item of iterator) {
+    promises.push(
+      fn(item).then(
+        () => null,
+        (err) => err ?? new Error('unknown error')
+      )
+    )
+  }
+  await Promise.all(
+    promises.map((promise) =>
+      promise.then((possibleErr) => {
+        if (possibleErr !== null) throw possibleErr
+      })
+    )
+  )
+}
+
+module.exports = {
+  asyncIteratorConcurrentProcess
+}