Fix source's error icon background
* Add spotless (with ktlint) * Run spotlessApply * screaming case screaming case screaming case * Update PagerViewerAdapter.kt * Update ReaderTransitionView.kt (cherry picked from commit d6252ab7703d52ecf9f43de3ee36fd63e665a31f)
* add countries flags add flags & simplify/sizing add flagkit * add flags to Extensions Filter * add flags to Sources & Extensions screen * show language flag in Library