Update README for syntax highlighting rules

README.md

@@ -109,10 +109,11 @@ providing further niceties.
 code = <<~CODE
   ```ruby
   def hello
-  puts "hello"
+    puts "hello"
   end
 CODE
 
+# pass in a theme name from a pre-existing set
 puts Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "InspiredGitHub" } })
 
 # <pre style="background-color:#ffffff;" lang="ruby"><code>
@@ -123,24 +124,32 @@ puts Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "Inspire
 # </code></pre>
 ````
 
-To disable this plugin, pass `nil`:
+By default, the plugin uses the `"base16-ocean.dark"` theme.
+
+To disable this plugin, set the value to `nil`:
 
 ```ruby
 Commonmarker.to_html(code, plugins: { syntax_highlighter: nil })
-# or
-Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: nil } })
 ```
 
-You can also provide a `path` to a directory containing `.tmtheme` files to load:
+To use CSS classes, set a key named `theme` to `nil`:
 
-```ruby
+````ruby
+code = <<~CODE
+  ```ruby
+  def hello
+    puts "hello"
+  end
+CODE
 
-Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "Monokai", path: "./themes" } })
-```
+Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "" } })
 
-##### Available themes
+# <pre class="syntax-highlighting"><code><span class="source ruby"><span class="meta function ruby"><span class="keyword control def ruby">def</span></span><span class="meta function ruby"> # <span class="entity name function ruby">hello</span></span>
+#   <span class="support function builtin ruby">puts</span> <span class="string quoted double ruby"><span class="punctuation definition string begin ruby">&quot;</span>hello<span class="punctuation definition string end ruby">&quot;</span></span>
+# <span class="keyword control ruby">end</span>\n</span></code></pre>
+````
 
-Here's [a list of themes available by default](https://docs.rs/syntect/5.0.0/syntect/highlighting/struct.ThemeSet.html#implementations):
+The library also comes with [a set of pre-existing themes:(https://docs.rs/syntect/5.0.0/syntect/highlighting/struct.ThemeSet.html#implementations) :
 
 - `"base16-ocean.dark"`
 - `"base16-eighties.dark"`
@@ -150,6 +159,18 @@ Here's [a list of themes available by default](https://docs.rs/syntect/5.0.0/syn
 - `"Solarized (dark)"`
 - `"Solarized (light)"`
 
+```ruby
+# pass in a theme name from a pre-existing set
+puts Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "InspiredGitHub" } })
+```
+
+To use a custome theme, you can provide a `path` to a directory containing `.tmtheme` files to load:
+
+```ruby
+
+Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "Monokai", path: "./themes" } })
+```
+
 ## Output formats
 
 Commonmarker can currently only generate output in one format: HTML.
@@ -198,3 +219,18 @@ Comparison:
 commonmarker with to_html:        5.8 i/s - 3.84x  (± 0.00) slower
             kramdown:        0.3 i/s - 68.30x  (± 0.00) slower
 ```
+
+```
+
+```
+
+````
+
+```
+
+```
+
+```
+
+```
+````