fix: conflict between browser URL object and Node URL object (#3061)

I am running this package using electron, what i noticed was that due to
the fact that the lines between node and browser environments become a
bit blurred, the URL class that was being used was the one defined by
the browser and not node. By making an explicit require it ensures the
correct Class is used.

While creating a test for this would be difficuilt i think adding an
eslint rule to stop using globally defined objects and require imports
instead would resolve issues like this in the future

packages/pg-connection-string/index.js

@@ -1,9 +1,9 @@
 'use strict'
-
 //Parse method copied from https://github.com/brianc/node-postgres
 //Copyright (c) 2010-2014 Brian Carlson (brian.m.carlson@gmail.com)
 //MIT License
 
+const { URL } = require('url')
 //parses a connection string
 function parse(str) {
   //unix socket