[Keyboard] Refactor Singa (#5579)

* pragma once it all

* put amnesia's name everywhere

* fixup readme

* remove custom matrix

* remove unneccessary configs

* disable bootmagic

* remove custom i2c in favor of i2c_master

* fix rgb led num

* add in rgb underglow support

keyboards/singa/readme.md

@@ -4,7 +4,7 @@
 ![Singa](https://i.imgur.com/VVO27Tr.jpg)
 
 
-A short description of the keyboard/project
+75% Custom Keyboard. 
 
 
 Keyboard Maintainer: [amnesia0287](https://github.com/amnesia0287)  
@@ -38,9 +38,9 @@ macOS:
     ```
 3. Install the following packages:
     ```
-    brew install python
-    brew install pyusb
-    brew install --HEAD`https://raw.githubusercontent.com/robertgzr/homebrew-tap/master/bootloadhid.rb
+    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.