Generate thumbnails before API starts up

Clients can now request a thumbnail by specifying a size on the image
request.

src/video.rs

@@ -1,5 +1,5 @@
-use std::process::Command;
 use std::path::Path;
+use std::process::Command;
 
 // ffmpeg -i test.mp4 -c:v h264 -flags +cgop -g 30 -hls_time 3 out.m3u8
 // ffmpeg -i "filename.mp4" -preset veryfast -c:v libx264 -f hls -hls_list_size 100 -hls_time 2 -crf 24 -vf scale=1080:-2,setsar=1:1 attempt/vid_out.m3u8
@@ -32,4 +32,3 @@ pub fn create_playlist(video_path: &str, playlist_file: &str) {
     println!("{:?}", result);
     println!("Status: {}", String::from_utf8(result.stdout).unwrap())
 }
-