doc: improve assert docs

[mscdex]

Checklist

• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

• doc

Description of change

Improve assert documentation by:

• Reorganizing link references
• Using consistent and concise language in function descriptions
• Documenting function parameters and return types

[mscdex]

/cc @nodejs/collaborators

[targos]

@nodejs/documentation

[Trott]

Nit: no scare quotes around strict equal

[thefourtheye]

Would Any be better instead of mixed?

[mscdex]

I used mixed because that is what I'm used to seeing in the online PHP documentation when they refer to a parameter that can be any or many different types. I figured other people coming from PHP might find that term more familiar than something else. shrug

[targos]

Closure and JSDoc use {*}

[Trott]

@mscdex Are you up for rebasing this?

[Trott]

Looks like most of these improvements or variations on them have already landed via other PRs. I'm going to go ahead and close this but absolutely feel free to re-open it if it's something you plan on rebasing and continuing to work on.