Add basic lua scripting capabilities (#4341)

The scripting capabilities is locked behind a cmake flag, and is not enabled by default.

Co-authored-by: nerix <nerixdev@outlook.de>
Co-authored-by: pajlada <rasmus.karlsson@pajlada.com>

src/singletons/Paths.hpp

@@ -34,6 +34,9 @@ public:
     // Profile avatars for Twitch <appDataDirectory>/cache/twitch
     QString twitchProfileAvatars;
 
+    // Plugin files live here. <appDataDirectory>/Plugins
+    QString pluginsDirectory;
+
     bool createFolder(const QString &folderPath);
     bool isPortable();