Added explicit error message for null or undefined matchers

[JoshuaKGoldberg]

What:

Added a nice explicit error message for the case in #717 of null or undefined as a matcher.

Why:

Better error messages = happier users! 💝

How:

Checklist:

• Documentation added to the
  docs site
• Tests
• Typescript definitions updated
• Ready to be merged
  

As before: I'm not attached to this particular error message, if a reviewer can think of something better that'd be nice.

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@f854cde). Click here to learn what that means.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             master      #718   +/-   ##
==========================================
  Coverage          ?   100.00%           
==========================================
  Files             ?        24           
  Lines             ?       635           
  Branches          ?       165           
==========================================
  Hits              ?       635           
  Misses            ?         0           
  Partials          ?         0           

Impacted Files	Coverage Δ
src/matches.js	100.00% <100.00%> (ø)
src/queries/display-value.js	100.00% <0.00%> (ø)
src/config.js	100.00% <0.00%> (ø)
src/screen.js	100.00% <0.00%> (ø)
src/role-helpers.js	100.00% <0.00%> (ø)
src/queries/alt-text.js	100.00% <0.00%> (ø)
src/queries/label-text.js	100.00% <0.00%> (ø)
src/queries/role.js	100.00% <0.00%> (ø)
src/queries/text.js	100.00% <0.00%> (ø)
... and 15 more

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[kentcdodds]

Looking great! Just one suggested change

[kentcdodds]

@all-contributors please add @JoshuaKGoldberg for code and tests

[allcontributors]

@kentcdodds

I've put up a pull request to add @JoshuaKGoldberg! 🎉

[kentcdodds]

🎉 This PR is included in version 7.21.5 🎉

The release is available on:

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

Your semantic-release bot 📦🚀