Fix mimetype for JS files (#532)

Author: wwwillchen

mesop/server/static_file_serving.py

@@ -1,5 +1,6 @@
 import gzip
 import io
+import mimetypes
 import os
 import re
 import secrets
@@ -17,6 +18,12 @@
 WEB_COMPONENTS_PATH_SEGMENT = "__web-components-module__"
 
 
+# mimetypes are not always set correctly, thus manually
+# setting the mimetype here.
+# See: https://github.com/google/mesop/issues/441
+mimetypes.add_type("application/javascript", ".js")
+
+
 def noop():
   pass