[Feature] Copy markdown linker with selected texts instead of original title

[realliyifei]

Now, this extension allows us to copy the markdown linker with the page title.

However, in lots of cases, we need to select some texts and attach them to the webpage link.

Therefore, it would be helpful to add one more feature: copying markdown linker with selected texts instead of the original title.

That is, we can select texts in a webpage first, then right-click as usual to select Copy Markdown Link, and a markdown linker combining selected texts and the webpage link will be generated in the clipboard.