Bump command ref to 5.4.0

[fflaten]

Fresh command reference docs based on the new Pester 5.4.0 release.
This includes a example changes and adds missing parameter-help, especially Should.mdx.

Fix pester/Pester#2128
Related pester/Pester#2170

[fflaten]

Needs a review, especially Should.mdx now that it's rendered and easier to have an opinion on the parameter help. Should we change the placeholder text (besides the \< \> glitch atm)?

Depends on operator being used. See Get-ShouldOperator -Name \<Operator\> for help.

[bravo-kernel]

Is <_<MethodName in https://github.com/pester/docs/blob/711d87076d113ca5742047d36bed52b671438201/docs/commands/New-MockObject.mdx correct?

Other than that, and the two parser bugs, this looks good to merge to me.

[bravo-kernel]

Thanks @fflaten and happy to see that there were only a few bumps with the parser 🎉