[Music] Add more music samples (shorter ones)

Add music from https://freemusicarchive.org.

Add a MUSIC_CREDITS file.

MUSIC_CREDITS

@@ -0,0 +1,29 @@
+All sample music in this repo has been sourced from Free Music Archive and from FreePD https://freepd.com
+https://freemusicarchive.org.
+
+Lukewarm Banjo by Kevin MacLeod
+Creative Commons CC BY 3.0
+https://creativecommons.org/licenses/by/3.0/
+
+Study and Relax by Kevin MacLeod | https://incompetech.com/
+Creative Commons CC BY 3.0
+Music promoted by https://www.chosic.com/free-music/all/
+
+Finally See The Light by Bryan Teoh
+Creative Commons CC BY NC "This music is available for commercial and non-commercial purposes."
+https://freepd.com/misc.php
+
+Neptunian Princess by Bryan Teoh
+Creative Commons CC BY NC "This music is available for commercial and non-commercial purposes."
+https://freepd.com/misc.php
+
+
+Future Technology Corporate instrumental | Business as Usual (short 4) by Alex-Productions
+Attribution-NonCommercial 4.0 International License. 
+https://freemusicarchive.org/music/alex-productions/corporate-instrumental-v2/future-technology-corporate-instrumental-business-as-usual-short-4/
+
+
+Tracks from the album "Microsong Challenge"
+Licensed under: CC0 1.0 Universal
+https://freemusicarchive.org/music/microSong_Challenge/2015021275957958
+

rs/tests/filemanager.rs

@@ -1,10 +1,10 @@
-use ::assert_matches::assert_matches;
+use assert_matches::assert_matches;
 use pickup::filemanager::{
     cache::{init, refresh},
     options::CollectionOptions,
 };
 
-const NUM_FILES: usize = 6;
+const NUM_FILES: usize = 33;
 
 #[test]
 fn test_refresh_and_load() {