Add config entry to specify cookie path

[ningw42]

browser_cookie3 fails to retrieve cookie of default profile for Chrome if there are multiple user profiles(on Darwin for me). however, browser_cookie3 does support specifying cookie path explicitly.

may be something like this:

let g:leetcode_browser='chrome'
let g:leetcode_cookie_path='path/to/profile/cookie.db'

or we can infer browser from cookie path, keeping one config entry

let g:leetcode_cookie_path='path/to/profile/cookie.db'

[ianding1]

Sure. I'll add this option soon.