Improve codeblock formatting in documentation

[jogly]

Improves codeblock highlighting by:

• Adding context to the codeblock detailing which language the following code is.
• Setting the pre block's background to match the default background for code blocks to give a consistent experience.
• Setting a border radius for the pre block double that of the code block's default (4px, which is hard-coded).

Works on class documentation blocks and li code blocks for properties/members/methods.

Before

After

[DaelonSuzuka]

That's awesome, thank you.