Allow to pass executablePath of browser in getOpenAIAuth

[MarvynSTAR]

As @luphoria pointed out in #140, using the library is tricky for those who for some reason don't have the browser in the default path. With this PR, I fixed this problem by adding the ability to pass the executablePath of the browser directly into the getOpenAIAuth function.

This helps users who use alternative versions of Chrome, who have installed it in a different path or who just want to use another browser.