[Keyboard] Pearl Refactors (#5907)

* use pragma once

* remove custom matrix

* remove custom i2c code in favor of QMK's i2c_master

* rename to all lower case readme

* update readme

* turn off bootmagic as it doesn't work anyway

* Update keyboards/pearl/readme.md

Co-Authored-By: noroadsleft <18669334+noroadsleft@users.noreply.github.com>

keyboards/pearl/readme.md

@@ -0,0 +1,47 @@
+# Pearl 40%
+
+Pearl 40% is a keyboard designed by Koobaczech. It uses an Atmel
+ATMEGA32A MCU.
+
+Keyboard Maintainer: [Ethan Madden](https://github.com/jetpacktuxedo)  
+Hardware Supported: Pearl  
+Hardware Availability: [Geekhack Group Buy](https://geekhack.org/index.php?topic=92259.0) 
+
+Make example for this keyboard (after setting up your build environment):
+
+    make pearl:default
+
+Flashing
+
+ps2avr(GB) boards use an atmega32a microcontroller and a different bootloader. It is not flashable using the regular QMK methods. 
+
+**Reset Key:** Hold down the key located at `K00`.
+
+Windows: 
+1. Download [HIDBootFlash](http://vusb.wikidot.com/project:hidbootflash).
+2. Place your keyboard into reset. 
+3. Press the `Find Device` button and ensure that your keyboard is found.
+4. Press the `Open .hex File` button and locate the `.hex` file you created.
+5. Press the `Flash Device` button and wait for the process to complete. 
+
+macOS:
+1. Install homebrew by typing the following:   
+    ```
+    /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+    ```
+2. Install `crosspack-avr`.  
+    ```
+    brew cask install crosspack-avr
+    ```
+3. Install the following packages:
+    ```
+    brew install python3
+    pip3 install pyusb
+    brew install --HEAD https://raw.githubusercontent.com/robertgzr/homebrew-tap/master/bootloadhid.rb
+    ```
+4. Place your keyboard into reset. 
+5. Flash the board by typing `bootloadHID -r` followed by the path to your `.hex` file. 
+
+**Please Note:** You will need to use the `EEP_RST` keycode first, followed by unplugging/replugging the board to get RGB underglow effects to work.
+
+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).