Floating comment button

[rugk]

It would be great if the comment button would only appear when text is selected.

So if the user selects some text a transparent version of the current button appears next to the selection. If the user hovers over this button it gets opaque and afterwards it just works as the current button.
When there is already a comment on a line the button could already become visible when hovering (not marking) the commented part, so that the user can instantly click on it and get to the reply box of the comment (so a click on the button, focuses this input field), type in the message and press enter to add a reply - without having to move the cursor to the right part of the screen.

This approach would have some advantages:

1. less need to move around the cursor around
2. intuitive
3. In the read-only mode the toolbar does not waste space as this is one of the few plugins, which have toolbar buttons in the read-only mode (so that there mostly is only one button in ro mode)

On https://medium.com you can e.g. find such a comment feature.