Improve error messages

[rluvaton]

What: Improve the error messages

Why: #732

How: updated the getMultipleError, getMissingError

Checklist:

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

Now, for custom matchers functions we would use the:

1. customMatcherText property on the function
2. the function name
3. [anonymous function]

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[eps1lon]

Looks like the changes are not fully covered by tests.

Can you structure this PR into multiple commits that make it easier to spot how error messages were changed (e.g. one commit with new tests and existing behavior and the next commit with changed behavior and updated tests)?

[rluvaton]

Hey, I did not finish (this is why I haven't checked the ready to merge checkbox) 😄
I'll convert this into a draft

[rluvaton]

@eps1lon for some reason the tests fail on get throws a useful error message › ByText › Multiple elements do you know why?

the snapshots are the same

also, how do you want me to organize my changes?

[rluvaton]

@eps1lon tagging you again in case you missed that