Edit initialization.md to auto-load code from the initialization.py example instead of manually copying it by hand

Author: tleonhardt

docs/features/initialization.md

@@ -2,94 +2,13 @@
 
 Here is a basic example `cmd2` application which demonstrates many capabilities which you may wish to utilize while initializing the app:
 
-```py
-    #!/usr/bin/env python3
-    """A simple example cmd2 application demonstrating the following:
-    1) Colorizing/stylizing output
-    2) Using multiline commands
-    3) Persistent history
-    4) How to run an initialization script at startup
-    5) How to group and categorize commands when displaying them in help
-    6) Opting-in to using the ipy command to run an IPython shell
-    7) Allowing access to your application in py and ipy
-    8) Displaying an intro banner upon starting your application
-    9) Using a custom prompt
-    10) How to make custom attributes settable at runtime.
-    """
+!!! example
 
-    from rich.style import Style
-
-    import cmd2
-    from cmd2 import (
-        Color,
-        stylize,
-    )
-
-
-    class BasicApp(cmd2.Cmd):
-        CUSTOM_CATEGORY = 'My Custom Commands'
-
-        def __init__(self) -> None:
-            super().__init__(
-                multiline_commands=['echo'],
-                persistent_history_file='cmd2_history.dat',
-                startup_script='scripts/startup.txt',
-                include_ipy=True,
-            )
-
-            # Prints an intro banner once upon application startup
-            self.intro = stylize(
-                'Welcome to cmd2!',
-                style=Style(color=Color.RED, bgcolor=Color.WHITE, bold=True),
-            )
-
-            # Show this as the prompt when asking for input
-            self.prompt = 'myapp> '
-
-            # Used as prompt for multiline commands after the first line
-            self.continuation_prompt = '... '
-
-            # Allow access to your application in py and ipy via self
-            self.self_in_py = True
-
-            # Set the default category name
-            self.default_category = 'cmd2 Built-in Commands'
-
-            # Color to output text in with echo command
-            self.foreground_color = Color.CYAN.value
-
-            # Make echo_fg settable at runtime
-            fg_colors = [c.value for c in Color]
-            self.add_settable(
-                cmd2.Settable(
-                    'foreground_color',
-                    str,
-                    'Foreground color to use with echo command',
-                    self,
-                    choices=fg_colors,
-                )
-            )
-
-        @cmd2.with_category(CUSTOM_CATEGORY)
-        def do_intro(self, _: cmd2.Statement) -> None:
-            """Display the intro banner."""
-            self.poutput(self.intro)
-
-        @cmd2.with_category(CUSTOM_CATEGORY)
-        def do_echo(self, arg: cmd2.Statement) -> None:
-            """Example of a multiline command."""
-            self.poutput(
-                stylize(
-                    arg,
-                    style=Style(color=self.foreground_color),
-                )
-            )
-
-
-    if __name__ == '__main__':
-        app = BasicApp()
-        app.cmdloop()
-```
+    ```py
+    {%
+        include "../../examples/initialization.py"
+    %}
+    ```
 
 ## Cmd class initializer