added coffeescript

Gemfile

@@ -33,3 +33,5 @@ gem "autoprefixer-rails", "~> 9.5"
 gem "image_optim", "~> 0.26.3"
 
 gem "image_optim_pack", "~> 0.5.2"
+
+gem "coffee-script", "~> 2.4"

Gemfile.lock

@@ -10,6 +10,10 @@ GEM
       public_suffix (>= 2.0.2, < 4.0)
     autoprefixer-rails (9.5.1.1)
       execjs
+    coffee-script (2.4.1)
+      coffee-script-source
+      execjs
+    coffee-script-source (1.12.2)
     colorator (1.1.0)
     concurrent-ruby (1.1.5)
     em-websocket (0.5.1)
@@ -112,6 +116,7 @@ PLATFORMS
 
 DEPENDENCIES
   autoprefixer-rails (~> 9.5)
+  coffee-script (~> 2.4)
   image_optim (~> 0.26.3)
   image_optim_pack (~> 0.5.2)
   jekyll (~> 3.8.5)

_assets/javascript/sequencer.coffee

@@ -0,0 +1 @@
+console.log "hello world"

_posts/sketches/2019-05-13-sequencer.markdown

@@ -5,6 +5,8 @@ date:   2019-05-12 09:16 +0800
 categories: toys
 ---
 {% asset sequencer.css %}
+{% asset sequencer.coffee %}
+
 <div class="sequencer-baseline" >
 	<div class="sequencer-wrapper" >
 		<div class="sequencer" >