feat: audio normalization

Closes #182

Signed-off-by: bggRGjQaUbCoE <githubaccount56556@proton.me>

lib/models/common/audio_normalization.dart

@@ -0,0 +1,12 @@
+enum AudioNormalization { disable, dynaudnorm, loudnorm, custom }
+
+extension AudioNormalizationExt on AudioNormalization {
+  String get title => ['禁用', '预设 dynaudnorm', '预设 loudnorm', '自定义参数'][index];
+  String get param => [
+        '',
+        // ref https://github.com/KRTirtho/spotube/commit/da10ab2e291d4ba4d3082b9a6ae535639fb8f1b7
+        'dynaudnorm=g=5:f=250:r=0.9:p=0.5',
+        'loudnorm=I=-16:LRA=11:TP=-1.5',
+        '',
+      ][index];
+}