Improving MIME type detection for some common file types when they are missing from the system MIME database

Also allow the user to specify their own database via mime.types in the
kitty config directory. See #3056

kittens/icat/main.py

@@ -3,7 +3,6 @@
 # License: GPL v3 Copyright: 2017, Kovid Goyal <kovid at kovidgoyal.net>
 
 import contextlib
-import mimetypes
 import os
 import re
 import socket
@@ -18,6 +17,7 @@ from typing import (
     Dict, Generator, List, NamedTuple, Optional, Pattern, Tuple, Union
 )
 
+from kitty.guess_mime_type import guess_type
 from kitty.cli import parse_args
 from kitty.cli_stub import IcatCLIOptions
 from kitty.constants import appname
@@ -273,7 +273,7 @@ def process(path: str, args: IcatCLIOptions, parsed_opts: ParsedOpts, is_tempfil
 def scan(d: str) -> Generator[Tuple[str, str], None, None]:
     for dirpath, dirnames, filenames in os.walk(d):
         for f in filenames:
-            mt = mimetypes.guess_type(f)[0]
+            mt = guess_type(f)
             if mt and mt.startswith('image/'):
                 yield os.path.join(dirpath, f), mt