Fix syntax error in object-copy article

[SpliceReborn]

The square brackets in 'Object.assign(dest, src1[, src2, src3...])'
results in a syntax error. The correct syntax should be
'Object.assign(dest, src1, src2, src3, ...)', but I've added a srcN, changing it
to 'Object.assign(dest, src1, src2, src3, ..., srcN)' to make it more relevant
to the explanation found underneath the original code snippet.

[CLAassistant]

All committers have signed the CLA.

[iliakan]

How shall we tell people that [...] is a special "cross-language" syntax for optional arguments?

The same question again and again...

[joaquinelio]

[ ] ...
play with size, font, color,
add as md.
color wont do well as editors highlight syntax that way,
but, maybe, grey and a little oversize will tell the brain there is smthing out of place

or,
you submit and use mdn way

[iliakan]

@joaquinelio You mean, write it as Object.assign(obj, ...sources)? May be a better choice, indeed! ;)

[joaquinelio]

oh!
It's an idea, a font that means it's not real code
far easier to implement.

I meant individual format
Object.assign(dest, src1 [ , src2, src3...] )
(well, I tricked it, the format should be in the brackets graying them, not the code)
Object.assign( dest, src1[, src2, src3...] )

[iliakan]

even if we make the brackets look different, people who don't know what they mean will still be confused.

[joaquinelio]

yep
more and more I'm convincing myself the [ ] is not a friendly tool for newcomers