Document how to suppress colorized output and summary line (#7448)

Fixes #7439.

Author: tapaswenipathak

docs/source/command_line.rst

@@ -503,6 +503,13 @@ in error messages.
 
         main.py:12:9: error: Unsupported operand types for / ("int" and "str")
 
+``--no-color-output``
+    This flag will disable color output in error messages, enabled by default.
+
+``--no-error-summary``
+    This flag will disable error summary. By default mypy shows a summary line
+    including total number of errors, number of files with errors, and number
+    of files checked.
 
 .. _incremental:
 

docs/source/config_file.rst

@@ -441,6 +441,11 @@ section of the command line docs.
 ``show_column_numbers`` (bool, default False)
     Shows column numbers in error messages.
 
+``color_output`` (bool, default True)
+    Shows error messages with color enabled.
+
+``error_summary`` (bool, default True)
+    Shows a short summary line after error messages.
 
 Advanced options
 ----------------