Add option to use fetched page title as title attribute

[xplosionmind]

According to the CommonMark specification, it is possible to add the title attribute to Markdown links.

Following this standard, it would be great if this plugin could fetch the title of the linked page and provide an option to inject it as the link title rather than the link text (or both).

If the user chooses to have the linked page’s title injected only within the title attribute and not as the text, two behaviors would be welcomed:

• the cursor is automatically moved inside the square brackets, so that the link text can be typed straight away
• if a text is already selected, and the link is “pasted into it”, then the selected text should not be overwritten, but rather become the effective text of the link.