Refactor parseArgs function in dialog module

[stevekinney]

I did a little bit of refactoring on the parseArgs helper function in the dialog module.

• When checking the last argument to see if it's a function, we access the array twice. I cached the argument into the variable in order to prevent that additional array access.
• I added destructuring for the argument shifting.
• In the conditional check to see if the first argument was a BrowserWindow, we were checking to see if window was null and then immediately checking it again in the ternary. We were also flipping the entire conditional after the fact. My thinking is that we could short-circuit using && and save the extra conditional check and then just check the constructor if it wasn't null. (I wonder if one call to Object.getPrototypeOf(window) would be a better approach?)

I wrote up some tests to verify that this all worked as I was going along, but parseArgs is a private helper and I didn't want to expose it as a public method, but I'm happy to figure out a way to include them if that's helpful.

[zcbenz]

Looks perfect to me ❤️ .