[feature] Finish work on Visual Selector "Select by style" implementation

Since the scraped data knows the styles of the elements on the page, the implementation of "select by style" needs to be finished

- Some "mode" button to switch between elements, or select by style
- Connect it with the notifications
- Maybe additionally specify a tag type like "`a`" so it will select all same style elements of `a`

Style = fontsize+fontcolor in this case.

So then the aim of the game, for example, is when you have a list of headings for products for sale, and you want to select just the headings and know when NEW headings arrive

Then in the notification, you can set it up to send all the HTML 's in the notification only

(extra points for making the `a href` in the notification be sure it has the https:// URL of the website incase it's relative!)

No files, tests, or entry points are named. Start by locating the existing Visual Selector and notification paths, then trace how scraped element styles are represented; done means a mode can select by style, optionally constrain by tag, notifications can emit matching HTML, and relative links are made absolute.

Written by the indexing model from the issue text.