Port keyboard input modules to Qt Quick and expand scope to cover input method configuration for System Settings

Users of Plasma Desktop Environment expect to find all their necessary system configurations through the System Settings application. So it plays an important role for the overall user experience of Plasma. But the current application is largely designed using the legacy QWidget framework, and does not meet the requirements for more responsive / modern design required for use in touch screens and mobile platforms. For that, it is necessary to port the KCMs to Qt Quick, which is quite tedious work and requires a lot of manpower. My primary goal is to help the KDE Community in this immense task, by porting the keyboard input modules, with modern designs provided by the KDE Visual Design Group (VDG).

Another additional goal is to integrate the input method configurations, such as ibus or fcitx, into the System Settings application. Currently, the only way to install / configure these input methods is to install it from a package manager and use the GUI provided by the input method, which is far from discoverable. The ability to add / remove and configure IMEs will improve user experience for a global audience.