Intergrate with null-ls using mason-null-ls

[nichtsam]

I've tried out the instruction in advance-usage.md, but the null-ls didn't get attached.
I investigated and play around for a bit, I found that I also need to add require("null-ls").setup() along with it, and then everything works.

I'm quite new at neovim and all the eco system, so I wonder if I misunderstood something or is the instruction missing a step?

just for reference, this is my nvim setup with working null-ls: https://github.com/nichtsam/nvim

[VonHeikemen]

The instruction is probably missing that step. I'll fix that later.