implement 'output.ansi' option (#2628)

docs/configuration.rst

@@ -2948,6 +2948,17 @@ Description
 .. __: `output.mode`_
 
 
+output.ansi
+-----------
+Type
+    ``bool``
+Default
+    ``false``
+Description
+    | On Windows, enable ANSI escape sequences and colored output
+    | by setting the ``ENABLE_VIRTUAL_TERMINAL_PROCESSING`` flag for stdout and stderr.
+
+
 output.skip
 -----------
 Type

docs/gallery-dl-example.conf

@@ -334,6 +334,9 @@
         "#": "while also considering wider East-Asian characters",
         "shorten": "eaw",
 
+        "#": "enable ANSI escape sequences on Windows",
+        "ansi": true,
+
         "#": "write logging messages to a separate file",
         "logfile": {
             "path": "~/gallery-dl/log.txt",

docs/gallery-dl.conf

@@ -355,6 +355,7 @@
         "mode": "auto",
         "progress": true,
         "shorten": true,
+        "ansi": false,
         "colors": {
             "success": "1;32",
             "skip"   : "2"