feat(about): show compiled short Git commit

lib/constants/app_info.dart

@@ -5,6 +5,10 @@ class AppInfo {
   static const String buildNumber = '143';
   static const String fullVersion = '$version+$buildNumber';
 
+  static const String gitCommit = String.fromEnvironment('GIT_COMMIT');
+  static String get shortGitCommit =>
+      gitCommit.length > 8 ? gitCommit.substring(0, 8) : gitCommit;
+
   static String get displayVersion => kDebugMode ? 'Internal' : version;
 
   static const String appName = 'SpotiFLAC Mobile';

lib/screens/settings/about_page.dart

@@ -223,7 +223,10 @@ class AboutPage extends StatelessWidget {
                 padding: const EdgeInsets.all(24),
                 child: Center(
                   child: Text(
-                    AppInfo.copyright,
+                    AppInfo.shortGitCommit.isEmpty
+                        ? AppInfo.copyright
+                        : '${AppInfo.copyright} · ${AppInfo.shortGitCommit}',
+                    textAlign: TextAlign.center,
                     style: Theme.of(context).textTheme.bodySmall?.copyWith(
                       color: colorScheme.onSurfaceVariant,
                     ),