feat(plugin-apidocs): improved method signature display

[sgtcoolguy]

Our current display of method signatures leaves out any means of marking varargs and optional args.

A quick few examples:

• a single optional vararg (optional: true, repeatable: true) should be:
  console.log([...data]) but is console.log(data)
• a single optional arg (optional: true) should be:
  console.log(data) but is console.log(data)
• a single vararg (repeatable: true) should be:
  console.log(...data) but is console.log(data)

There's more complex cases like multiple optional arguments:

• for example, Node shows:
  util.inspect(object[, showHidden[, depth[, colors]]])
  As you can see, they typically nest the optional brackets. There's other cases where they don't:
  console.timeLog([label][, ...data])
  It's not clear to me if they don't nest when the last optional arg is varargs, or in other cases too? (We don't really have a means of relating optional arguments to one another in our doc structure to control nesting here)

[sgtcoolguy]

Seems like Node.js is inconsistent with regard to multiple optional arguments. In assert docs, they don't nest the brackets:
assert.doesNotReject(asyncFn[, error][, message])

So again, it's not real clear to me when they should be nested vs not. I assume it's when ordering/count matters (i.e. for util.inspect you must supply an argument, possibly undefined for showHidden and supply depth as the 3rd arg - whereas with assert.doesNotReject it may support message as the second arg?)