Add separator option

[janosrusiczki]

Do you think it would be a good idea to have a separator option?

It would work as follows:

pageTitle({
  suffix: 'The Best Page On The Internet',
  separator: ' - ',
})

The page title will be:

• 'The Best Page On The Internet' for useTitle(ref(''))
• 'Photos - The Best Page On The Internet' for useTitle(ref('Photos'))

So it doesn't add the separator if the title is blank. I see this as useful for homepages or for pages that get their title asynchronously.