docs: add className in documentation

Author: jy95

testsite/docs/api/JSONSchemaViewer.mdx

@@ -13,6 +13,7 @@ import TabItem from '@theme/TabItem';
 | schema          | JSONSchema    | Mandatory   | JSON Schema Draft-07 / Draft 2019-09 / Draft 2020-12    |
 | resolverOptions | IResolveOpts  | Optional    | To resolve your $ref (by default, only inline references will be dereferenced). |
 | viewerOptions   | JSVOptions    | Optional    | Options for the viewer itself. |
+| className       | string        | Optional    | To customize the styles of the viewer, to override docusaurus styles on a specific page |
 
 ### Types