Add python3-setuptools to apt line
This is only a "recommends" in Debian stable/Ubuntu LTS so may not get installed automatically (#287)

docs/Linux.md

diff --git a/docs/Linux.md b/docs/Linux.md
index 56a0af0..813f9dc 100644
--- a/docs/Linux.md
+++ b/docs/Linux.md
@@ -26,7 +26,7 @@
 New enough versions of these exist in at least Debian "buster" and Ubuntu 20.04.
 
 ```
-sudo apt install git gcc g++ gcc-arm-none-eabi cmake make python3 python3-pip libsdl2-dev libsdl2-image-dev libsdl2-net-dev unzip
+sudo apt install git gcc g++ gcc-arm-none-eabi cmake make python3 python3-pip python3-setuptools libsdl2-dev libsdl2-image-dev libsdl2-net-dev unzip
 
 pip3 install 32blit
 ```

docs/Windows-WSL.md

diff --git a/docs/Windows-WSL.md b/docs/Windows-WSL.md
index ca53ba3..a49b09d 100644
--- a/docs/Windows-WSL.md
+++ b/docs/Windows-WSL.md
@@ -34,7 +34,7 @@
 (These are similar to the [Linux requirements](Linux.md#prerequisites), see those for more details)
 
 ```
-sudo apt install gcc gcc-arm-none-eabi unzip cmake make python3 python3-pip
+sudo apt install gcc gcc-arm-none-eabi unzip cmake make python3 python3-pip python3-setuptools
 pip3 install 32blit construct bitstring
 ```