Add option to flash white screen on page change in reader for e-ink displays

Closes #2123

app/src/main/java/eu/kanade/presentation/reader/DisplayRefreshHost.kt

@@ -0,0 +1,45 @@
+package eu.kanade.presentation.reader
+
+import androidx.compose.foundation.Canvas
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.Stable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import kotlinx.coroutines.delay
+
+@Stable
+class DisplayRefreshHost {
+
+    internal var currentDisplayRefresh by mutableStateOf(false)
+
+    fun flash() {
+        currentDisplayRefresh = true
+    }
+}
+
+@Composable
+fun DisplayRefreshHost(
+    hostState: DisplayRefreshHost,
+    modifier: Modifier = Modifier,
+) {
+    val currentDisplayRefresh = hostState.currentDisplayRefresh
+    LaunchedEffect(currentDisplayRefresh) {
+        if (currentDisplayRefresh) {
+            delay(200)
+            hostState.currentDisplayRefresh = false
+        }
+    }
+
+    if (currentDisplayRefresh) {
+        Canvas(
+            modifier = modifier.fillMaxSize(),
+        ) {
+            drawRect(Color.White)
+        }
+    }
+}

app/src/main/java/eu/kanade/presentation/reader/settings/GeneralSettingsPage.kt

@@ -68,4 +68,9 @@ internal fun ColumnScope.GeneralPage(screenModel: ReaderSettingsScreenModel) {
         label = stringResource(R.string.pref_page_transitions),
         pref = screenModel.preferences.pageTransitions(),
     )
+
+    CheckboxItem(
+        label = stringResource(R.string.pref_flash_page),
+        pref = screenModel.preferences.flashOnPageChange(),
+    )
 }