Resolve the Favicon for newly added bookmarks on synchronization

### Describe the feature you'd like to request

When synchronizing new bookmarks on systems that haven't visited the particular site the favicon or site icon is not resolved. The same is true for a complete new setup where none of the sites where ever visited.

As my bookmark archive grows opening every single site on a reinstall or a merge from a different system is painstakingly time consuming process. I think this is probably a feature that a lot of people are looking for.

A quick overview of the code seems like there is already a class getFavicon that seems to do just that. It is a class from 5 years ago.

I added this as feature request and not a bug fix because I could find a definitive answer if this is already implemented. I tested it for firefox and chrome and there it doesn't seem to work.

Thanks in advance. ;)

### Describe the solution you'd like

After a synchronization if a new bookmark is added the site icon is looked up and show in the bookmarks menu or bookmarks toolbar

### Describe alternatives you've considered

I looked up and tested some plugins that may also implement this behavior specifically for the resolve of the icons but none seem to offer that functionality. And you can't seem to trigger it from the browser settings at least not for Firefox and Chrome.

Start by locating the existing getFavicon class and tracing the synchronization path for newly added bookmarks. Verify the behavior in Firefox and Chrome with a bookmark from a site not previously visited; done means its site icon is resolved and shown in the bookmarks menu or toolbar after synchronization.

Written by the indexing model from the issue text.