fix(TS): declare first parameter of screen.debug as optional

[simrobin]

What: Typings of screen.debug helper does not reflect prettyDOM signature

Why: Prevent this kind of error when calling screen.debug() without params from a typescript file:

node_modules/@testing-library/dom/types/screen.d.ts:11:9
11         element: Element | HTMLDocument | Array<Element | HTMLDocument>,
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
An argument for 'element' was not provided.

How: Updated typings

Checklist:

• Documentation added to the
  docs site N/A but the doc already mention that we can use screen.debug()
• I've prepared a PR for types targeting
  DefinitelyTyped <- Is this still maintained since it was migrated to this repo?
• Tests N/A
• Ready to be merged
  

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[codecov]

Codecov Report

Merging #573 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #573   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           23        23           
  Lines          462       462           
  Branches       114       114           
=========================================
  Hits           462       462           

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[kentcdodds]

Ah yes, thank you 👍

[kentcdodds]

🎉 This PR is included in version 7.5.5 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀