add way to reduce build output's size

(cherry picked from commit 5231f54c27)

readme.md

@@ -20,6 +20,9 @@ It also convert the PPM assets (map and sprites) into ASM raw values representat
 Usage example:
 ```sh
 ./build.ts > /path/to/the/game/schematics/architecture/Symfony/sandbox/main.asm
+
+# script output can easily be piped to strip it off all comments, leading whitespace and empty lines:
+./build.ts | sed 's/\s*;.*//' | sed 's/^\s*//' | sed '/^\d*$/d' > result.asm
 ```
 
 The script is build over Deno's API, so you'll need to have a `deno` binary in your PATH to use it that way.