Added customization page

docs/docs/customization.md

@@ -0,0 +1,33 @@
+---
+id: customization
+title: Customizing ZMK
+sidebar_label: Customizing ZMK
+---
+
+After verifying you can successfully flash the default firmware, you will probably want to begin customizing your keymap and other keyboard options.
+
+## Configuration Changes
+
+The setup script creates a `config/<shield>.conf` file that allows you to add additional configuration options to
+control what features and options are built into your firmware. Opening that file with your text editor will allow you to see the
+various config settings that can be commented/uncommented to modify how your firmware is built.
+
+## Keymap
+
+Once you have the basic user config completed, you can find the keymap file in `config/<shield>.keymap` and customize from there.
+Refer to the [Keymap](/docs/feature/keymaps) documentation to learn more.
+
+## Publishing
+
+After making any changes you want, you should commit the changes and then push them to GitHub. That will trigger a new
+GitHub Actions job to build your firmware which you can download once it completes.
+
+:::note
+If you need to, a review of [Learn The Basics Of Git In Under 10 Minutes](https://www.freecodecamp.org/news/learn-the-basics-of-git-in-under-10-minutes-da548267cc91/) will help you get these steps right.
+:::
+
+## Flashing Your Changes
+
+For normal keyboards, follow the same flashing instructions as before to flash your updated firmware.
+
+For split keyboards, only the central (left) side will need to be reflashed if you are just updating your keymap.