Use enhanced-resolve for module resolution when using DtsPackPlugin.
The package 'enhanced-resolve' with version 2.0.0 or higher (currently up to 4.x) is necessary when using the plugin. Users are possibly unnecessary to install it explicitly because webpack and/or other loaders use it.
Note that this change does not affect the command-line or APIs; when using dts-pack from command-line or APIs, 'enhanced-resolve' is not used.