Add more thumbnails for more mimetypes that we don't generate thumbanils for (wav, zip, things like that)

script.js

@@ -500,6 +500,17 @@ function caught(m, e) {
     alert(new Error(m + e.message));
 };
 
+const MIME_THUMBNAILS = {
+    'audio/opus':      '/static/mpg.png',
+    'audio/ogg':       '/static/mpg.png',
+    'audio/wav':       '/static/wav.png',
+    'audio/x-wav':     '/static/wav.png',
+    'audio/mpeg':      '/static/mpg.png',
+    'application/zip': '/static/zip.png',
+    'text/plain':      '/static/txt.png',
+    'application/x-7z-compressed' : '/static/7z.png'
+};
+
 function mkSpamImgElement(img_description) {
     var img_elem = document.createElement('img');
     var mime = img_description.mimetype;
@@ -510,8 +521,8 @@ function mkSpamImgElement(img_description) {
 
     if (illegal) {
         thumb_url = "/static/redacted.jpg";
-    } else if (mime == "audio/mpeg") {
-        thumb_url = '/static/mpg.png';
+    } else if (MIME_THUMBNAILS[mime] != null) {
+        thumb_url = MIME_THUMBNAILS[mime];
     } else {
         thumb_url = `/bin/?path=${img_description.md5_hash}_thumbnail.jpg&mimetype=image/jpeg`
     }