new: add theme support with GwenedegTheme to take dark mode into account

shared/src/commonMain/kotlin/fr/ajaury/gwenedeg/App.kt

@@ -1,6 +1,5 @@
 package fr.ajaury.gwenedeg
 
-import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.mutableStateListOf
 import androidx.compose.runtime.saveable.rememberSerializable
@@ -12,6 +11,7 @@ import fr.ajaury.gwenedeg.di.appModule
 import fr.ajaury.gwenedeg.navigation.Route
 import fr.ajaury.gwenedeg.player.ui.PlayerScreen
 import fr.ajaury.gwenedeg.records.ui.RecordsScreen
+import fr.ajaury.gwenedeg.theme.GwenedegTheme
 import org.koin.compose.KoinApplication
 import org.koin.dsl.koinConfiguration
 
@@ -28,7 +28,7 @@ fun App() {
             mutableStateListOf(Route.Records)
         }
 
-        MaterialTheme {
+        GwenedegTheme {
             NavDisplay(
                 backStack = backStack,
                 onBack = { backStack.removeLastOrNull() },

shared/src/commonMain/kotlin/fr/ajaury/gwenedeg/theme/Theme.kt

@@ -0,0 +1,23 @@
+package fr.ajaury.gwenedeg.theme
+
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.darkColorScheme
+import androidx.compose.material3.lightColorScheme
+import androidx.compose.runtime.Composable
+
+private val DarkColorScheme = darkColorScheme()
+private val LightColorScheme = lightColorScheme()
+
+@Composable
+fun GwenedegTheme(
+    darkTheme: Boolean = isSystemInDarkTheme(),
+    content: @Composable () -> Unit,
+) {
+    val colorScheme = if (darkTheme) DarkColorScheme else LightColorScheme
+
+    MaterialTheme(
+        colorScheme = colorScheme,
+        content = content,
+    )
+}