Added file extension constant and updated constants module

src/constants.rs

@@ -1,5 +1,15 @@
+
+pub mod file_extensions {
+    pub mod audio {
 pub const DEFAULTMUSICEXTENSION: &str = FLACEXTENSION;
 pub const FLACEXTENSION: &str = ".flac";
 pub const WAVEXTENSION: &str = ".wav";
 pub const MPTHREEEXTENSION: &str = ".mp3";
+    }
+
+    pub mod image {
 pub const JPGEXTENSION: &str = ".jpg";
+pub const JPEGEXTENSION: &str = ".jpeg";
+pub const PNGEXTENSION: &str = ".png";
+    }
+}