docs: improve Windows setup instructions for TextTest with Python

Fixes issue where newer versions of texttest produce .exe files instead of .py files. Updated start_texttest_from_python.bat to use texttestc.exe instead of texttestc.py. Also enhanced documentation for Windows users with recommendations for tools like Meld and fc.

texttests/config.gr

@@ -3,6 +3,8 @@ full_name:Gilded Rose Refactoring Kata
 # set your preferred editor and diff tool.
 view_program:subl
 diff_program:meld
+#text_diff_program:fc
+
 
 # Settings for the Python version
 #executable:${TEXTTEST_HOME}/python/texttest_fixture.py