doc: mention prototype check in deepStrictEqual()

[cjihrig]

The docs for assert.deepStrictEqual() do not currently mention that prototypes are compared for objects. This commit adds that information to the documentation.

Fixes: #5365

[cjihrig]

R=@nodejs/documentation

[eljefedelrodeodeljefe]

LGTM

[benjamingr]

I'm not sure I would understand what "object prototypes are included in the comparison" means - it might imply they need to have the same __proto__.

[cjihrig]

What about this?

Generally identical to `assert.deepEqual()` with two exceptions. First, primitive values are compared using the strict equality operator ( `===` ). Second, object comparisons include a strict equality check of their prototypes. 

[benjamingr]

That might still imply that their prototypes are checked and are expected to be equal (is that the case?) - what about:

Generally identical to assert.deepEqual() with two exceptions. First, primitive values
are compared using the strict equality operator ( === ). Second, object comparisons
include a strict equality check of properties on their prototypes.

[cjihrig]

It's actually a strict comparison of the prototypes. https://github.com/nodejs/node/blob/master/lib/assert.js#L199

[benjamingr]

@cjihrig Oh, in that case my bad - LGTM

[thefourtheye]

object prototypes are included in the comparison.

seems a little vague to me.

[cjihrig]

See proposed change in the main thread.

[thefourtheye]

it would have been better if we could somehow say that prototypes should be the same. But yeah the proposed change also is okay.

[thefourtheye]

LGTM

[cjihrig]

Thanks for the reviews. Landed in 10f55b0.