feat: Configure pixel ID used based on router path

[niklasfjeldberg]

Some people may want that another pixel than the default to be used on a specific path. Although you can do this manually, this should be easily done trough the config file.

pixels: [{
  id: 'xxxxx',
  path: '/page2'
}, {
  id: 'xxxxx',
  path: '/page4'
}]