Docs: Update TypeScript.md

[osmolyar]

Proposed changes

Update Docs: TypeScript.md section on config file for using typed wdio.config file t

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ x] Documentation update

Checklist

• [x ] I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• [x ] I have added necessary documentation (if appropriate)
• I have added proper type definitions for new commands (if appropriate)

Further comments

This was necessary because otherwise index.d.ts or other standalone type definition files don't get recognized by the ts-node compiler if a typed config is used.

Reviewers: @webdriverio/project-committers

[jsf-clabot]

All committers have signed the CLA.