Remove valid-url package and usage throughout tree

[humphd]

We have a bunch of places in the project that use the https://www.npmjs.com/package/valid-url package. This code hasn't been updated in 8 years, and is totally unnecessary in modern browsers and node, which both ship a URL parser:

• browser: https://developer.mozilla.org/en-US/docs/Web/API/URL
• node: https://nodejs.org/api/url.html

Let's drop this dependency and switch to using the maintained URL() function.

[menghif]

I would like to work on this :)

[manekenpix]

@menghif All yours!