Update README

Author: r-sierra

Diff for: README.md

@@ -286,8 +286,10 @@ The `tailwindcss:build` task is automatically attached to the `test:prepare` Rak
 
 ### Building unminified assets
 
-If you want unminified assets, you can pass a `debug` argument to the rake task, i.e. `rails tailwindcss:build[debug]` or `rails tailwindcss:watch[debug]`.
+If you want unminified assets, you can:
 
+- pass a `debug` argument to the rake task, i.e. `rails tailwindcss:build[debug]` or `rails tailwindcss:watch[debug]`.
+- set an environment variable named `TAILWINDCSS_DEBUG` with a value of `true` or `1` 
 
 ### Live rebuild