Display minimal diagnostics aside the line numbers

[mkermani144]

Why

I don't know about the others, but for me, it happens a lot that I see there is an error in some file. I open the file, and using the minimap, I scroll down to the error location. But I cannot spot the error quickly: the red line indicating the error doesn't catch my eyes. I know that my theme plays a big role here, but I still think it's not the only reason. Here is an example of an error that I cannot see quickly:

What

I have seen some Vim folks have their code diagnostics shown aside the line numbers. I'm not sure if this is a feature of (Neo)Vim or its plugins. (It may be "diagnostic signs" config of nvim, but I'm not sure.) I'm not an average Vim user btw. Here is an example I found on GitHub:

How

Whether it's showing some letters (e.g. a red "E" for errors, etc.) or indicators (e.g. a red "close" icon), colorizing the line number, or some other method, they all help.