fix: allow plugins to have scope

[dubisdev]

About the regex:

• If base (the folder to treat as a plugin) matches node_modules or a scope (@) named folder, returns, as they must not be loaded as plugins. --> Ignore node_modules as the folder that should load is /node_modules/plugin-folder or /@scope/plugin-name

• Dir (the parent folder of the plugin folder) must be node_modules or a scope named folder (to ignore scanned folders inside a plugin) --> Ignore /plugin-folder/subfolder as the plugin must be required from the root folder of the plugin

fix #468

[dubisdev]

This PR is ready now!

In future iterations it would be nice to refactor readdir, readfile... to their async methods to avoid performance issues.