[FR]: New example for mixed JS/TS project

### What is the current behavior?

Currently there is an example that used to be in JavaScript and the entire example was migrated to TypeScript.

### Describe the feature

I think it would be great to have an example that shows how to get a project configured that is partially partially in TypeScript and JavaScript as this would give guidance to people who currently have projects undergoing TypeScript migrations.

Or perhaps just add more details in the existing example that discusses best practices for projects undergoing a TypeScript migration.

Start by reviewing the existing example that was migrated from JavaScript to TypeScript and how its project configuration is documented. Decide whether to add a separate mixed JavaScript/TypeScript example or expand the existing one; done means the repository includes clear guidance for projects undergoing a TypeScript migration.

Written by the indexing model from the issue text.