Add ability to add other classes to the :syntax plugin

[donnfelker]

Add the ability to provide additional classes to the <pre> tag.

Usage:

activate :syntax, :classes => ['not-prose']

Use Case:
When you're rendering code inside of tailwind typography prose classes, which we do in RubyStaticPro prose will try to take over the rendering of the code block. To stop this from happening you can apply the not-prose class and tailwindcss typography will not format it. See docs here

This update allows you to provide additional classes that will be rendered to the <pre> tag.

In the config.rb

activate :syntax, :classes => ['not-prose']

Result:

<div class="highlight">
-  <pre class="highlight ruby">...</pre>
+  <pre class="highlight ruby not-prose">...</pre>
</div>

[markets]

Thanks @donnfelker! Just added a couple of minor comments, but +1 for the feature 👍

[markets]

Thanks @donnfelker! Test failures are unrelated, fixed them on master (5ca4c2a).

[donnfelker]

Fantastic! Thanks for accepting the PR 🎉

[markets]

@donnfelker New version pushed to RubyGems: https://rubygems.org/gems/middleman-syntax/versions/3.5.0 🎉

[donnfelker]

Thank you so much!