allow to set url

so you can run electra on existing pages too. api could be

```js
electra('https://google.com/', `
do(this)
`)
```

or maybe

```js
electra(`
if (location !== 'https://google.com/') location = 'https://google.com/'
do(this)
`)
```

Start by locating the public electra(...) entry point and the existing code path that runs snippets inside Electron. Compare the two proposed URL APIs, determine the intended behavior for existing pages, and define completion with a focused test or example covering navigation to the requested URL.

Written by the indexing model from the issue text.