Added documentation for defaultLanguage setting in the CodeBlock extension

[AbhayVAshokan]

• fix: respect defaultLanguage on code-block-lowlight add option to code-block tiptap#5406 introduced the defaultLanguage setting for the CodeBlock extension as a bug fix. The objective of this PR is to add documentation this change.

---

The following code snippet demonstrates how to specify the defaultLanguage setting.

CodeBlock.configure({
  defaultLanguage: '<lang>',
})

When the defaultLanguage setting is specified, it will add a class of the format language-<lang> to the <code> tag. The prefix (language-) can be further customized using the languageClassPrefix setting.

I am attaching a CodeSandbox link where the same can be verified: https://codesandbox.io/p/sandbox/codeblock-tiptap-387xqm

[vercel]

@AbhayVAshokan is attempting to deploy a commit to the Tiptap Team on Vercel.

A member of the Team first needs to authorize it.

[nperez0111]

Appreciate the contribution!