clean up dynamic plugin loading

Summary:
There are 3 sources where plugins can be loaded from:
* `src/plugins`
* `src/fb/plugins`
* any path specified in `~/.sonar/config.json`

Plugins found in the first two directories are bundled with the app when building.

Reviewed By: jknoxville

Differential Revision: D8636061

fbshipit-source-id: 2064090d43d11695ffd99df195e5b594559fe087

src/utils/isProduction.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright 2018-present Facebook.
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ * @format
+ */
+
+import electron from 'electron';
+
+const _isProduction = !/node_modules[\\/]electron[\\/]/.test(
+  electron.remote.process.execPath,
+);
+
+export default function isProduction(): boolean {
+  return _isProduction;
+}