Add Erlang to BUILD-MAC.md, update GitHub target

s/samaaron/sonic-pi-net/g

Also, `erlang` is a dependency that was unlisted.

Author: xavriley

BUILD-MAC.md

@@ -10,7 +10,7 @@ version of Sonic Pi. If you're just looking to install it, we've already
 done all of this work for you and you can grab the latest signed
 pre-built version of the app here:
 
-https://github.com/samaaron/sonic-pi/releases
+https://github.com/sonic-pi-net/sonic-pi/releases
 
 If you're definitely sure you want to build your own release, then we
 really hope that these instructions help. Please let us know if you have
@@ -39,7 +39,7 @@ few dependencies:
 
 1. Xcode (12.1+) and command line tools
 2. Homebrew
-3. All other dependencies - Qt (5.15+), CMake (3.18+)
+3. All other dependencies - Qt (5.15+), CMake (3.18+), Erlang (23.1.1+)
 
 ### 1.1 Install Xcode
 
@@ -68,7 +68,7 @@ Once you have Homebrew installed, pulling in the rest of the
 dependencies is a couple of lines to execute within a terminal:
 
 ```
-brew install qt cmake
+brew install qt cmake erlang
 
 ```
 
@@ -81,14 +81,14 @@ The easiest way of getting this is likely to be cloning from GitHub
 into a folder on your hard drive such as `~/Development/sonic-pi`:
 
 ```
-git clone https://github.com/samaaron/sonic-pi.git ~/Development/sonic-pi
+git clone https://github.com/sonic-pi-net/sonic-pi.git ~/Development/sonic-pi
 ``` 
 
 If you don't have Git installed you should be able to download a `.zip`
 file of the latest commit or specific release (v3.3+) you'd like to
 build:
 
-https://github.com/samaaron/sonic-pi/archive/main.zip
+https://github.com/sonic-pi-net/sonic-pi/archive/main.zip
 
 From now on these instructions will assume you downloaded the source 
 into `~/Development/sonic-pi`. If you used a different location be sure to