[docs:options] add --update arguments

docs/options.md

@@ -6,6 +6,9 @@
 ## General Options:
     -h, --help                  Print this help message and exit
     --version                   Print program version and exit
+    -U, --update                Update to the latest version
+    --update-to [CHANNEL@]TAG   Upgrade/downgrade to a specific version
+    --update-check              Check if a newer version is available
     -f, --filename FORMAT       Filename format string for downloaded files
                                 ('/O' for "original" filenames)
     -d, --destination PATH      Target location for file downloads

scripts/options.py

@@ -14,7 +14,10 @@ import re
 import sys
 
 import util
-from gallery_dl import option
+
+import gallery_dl.util
+gallery_dl.util.EXECUTABLE = True
+from gallery_dl import option  # noqa E402
 
 
 TEMPLATE = """# Command-Line Options