Display the nth relative number in the signs bar

This script display the 10nth lines before and after the current cursor row position. It comes from a this question.

The core concept behind it comes directly from the vim-signature plugin. Here is a step-by-step walkthrough :

1. Remove all previous signs from the sign bar
2. Build a list of the lines you want to show in the sign bar
3. For each line, create a new sign with a unique id (based on current buffer and line number)
4. For each line, display the sign (the text of the sign will be the current line)

This script works as a proof of concept, but I wouldn't use is. You will see if you try it that it gets all flickering when you move quickly. I think the reason behind it is that the sign bar is not intended to quickly change over time.

If you want to see this code evolve and maybe become a plugin, you can reach via an issue. Thanks !