[🐛 Bug]: Typescript support for Custom matchers seems broken with V9

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

WebdriverIO Version

V9

Node.js Version

20

Mode

WDIO Testrunner

Which capabilities are you using?

No response

What happened?

When creating a new customer matcher and you want to use ExpectWebdriverIO.PartialMatcher you get a TS error Namespace 'global.ExpectWebdriverIO' has no exported member 'PartialMatcher'. This prevents the Visual Testing Service to upgrade to V9 without using a workaround. See also https://github.com/webdriverio/visual-testing/actions/runs/10442443274/job/28914748091?pr=417

What is your expected behavior?

No response

How to reproduce the bug.

Clone the Visual project and use this PR

Relevant log output

Namespace 'global.ExpectWebdriverIO' has no exported member 'PartialMatcher'

Code of Conduct

• I agree to follow this project's Code of Conduct

Is there an existing issue for this?

• I have searched the existing issues

Clone the Visual project and use the reproduction described in PR 417 to observe the TypeScript error for ExpectWebdriverIO.PartialMatcher. Trace the relevant WebdriverIO type declarations and confirm that the Visual Testing Service can upgrade to V9 without the reported namespace error.