Updated documentation for new BDN9 board revisions (#11380)

Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: Danny <nooges@users.noreply.github.com>

keyboards/keebio/bdn9/readme.md

@@ -2,14 +2,27 @@
 
 ![BDN9](https://cdn.shopify.com/s/files/1/1851/5125/products/image_bd8d9423-950e-4aad-bea5-665d896f879a_530x@2x.jpg?v=1547909493)
 
-A 3x3 macropad with support for a rotary encoder at the upper two corners.
+A 3x3 macropad with support for up to 3 rotary encoders.
 
-Keyboard Maintainer: [Bakingpy/nooges](https://github.com/nooges)  
-Hardware Supported: Pro Micro, Elite-C, Proton C   
-Hardware Availability: [Keebio - BDN9](https://keeb.io/products/bdn9-3x3-9-key-macropad-rotary-encoder-support) 
 
-Make example for this keyboard (after setting up your build environment):
+* Rev. 1.0-1.2 encoder locations: Top Right, Top Left
+* Rev. 1.3 encoder locations: Top Right, Top Middle, Top Left
+* Rev. 2 encoder locations: Top Right, Top Middle, Top Left
+
+
+**Keyboard Maintainer:** [Bakingpy/nooges](https://github.com/nooges)
+
+**Hardware Supported:**
+* Rev. 1: Pro Micro, Elite-C, Proton C
+* Rev. 2: Integrated STM32F072 microcontroller
+
+**Hardware Availability:**
+* [Keebio - BDN9 Rev. 1](https://keeb.io/products/bdn9-3x3-9-key-macropad-rotary-encoder-support)
+* [Keebio - BDN9 Rev. 2](https://keeb.io/products/bdn9-rev-2-3x3-9-key-macropad-rotary-encoder-and-rgb)
+
+Make examples for this keyboard (after setting up your build environment), select the appropriate line for your PCB revision:
 
     make keebio/bdn9/rev1:default
+    make keebio/bdn9/rev2:default
 
 See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).