docs: improve version docs

Author: Rel1cx

website/pages/docs/configuration.mdx

@@ -31,7 +31,8 @@ This should not be a member expression (i.e. use `"Fragment"` instead of `"React
 
 (type: `string`, default: `"detect"`)
 
-React version to use, `"detect"` means auto detect React version from the project's dependencies.
+React version to use, `"detect"` means auto detect React version from the project's dependencies.\
+If `importSource` is specified, an equivalent version of React should be provided here.
 
 ### `additionalHooks`