Enable JIT compiler for Tailwind

Ok that turned out to be easier than expected. A bit of Googling lead to
a blog post where someone mentioned to do this, and now it works!

Author: nickjj

CHANGELOG.md

@@ -29,6 +29,7 @@ Changelog](https://keepachangelog.com/en/1.0.0/).
 - Update PostgreSQL from `13.2` to `13.3`
 - Update Redis from `6.0.10` to `6.2.3`
 - Use new packs directory structure recommended by Webpacker 6
+- Enable JIT compiler for TailwindCSS
 - Move `tailwind.config.js` to the root of the project
 
 ### Fixed

config/application.rb

@@ -35,3 +35,6 @@ class Application < Rails::Application
     config.action_cable.allowed_request_origins = origins
   end
 end
+
+# Ensure the TailwindCSS JIT compiler exits properly.
+Webpacker::Compiler.env["TAILWIND_MODE"] = "build"

tailwind.config.js

@@ -1,5 +1,5 @@
 module.exports = {
-  //mode: "jit",
+  mode: "jit",
   purge: {
     enabled: ["production"].includes(process.env.NODE_ENV),
     content: [