feat: add `ignore_methods` to ignore setup of null-ls source method types

A lot more people nowadays are starting to use more tools like conform or nvim-lint and things which replace certain functionality in null-ls but not all of it. It might be a good idea to add the ability to ignore types by default. Like if I'm using conform and still want to rely on mason-null-ls for diagnostics and code actions, I could add to the setup like ignore_methods = { "formatting" } since that's handled by conform. Or if I use both conform and nvim-lint but want to use null-ls for code actions, adding ignore_methods = { "formatting", "diagnostics" } which won't add those types to the handlers when they are called.

Update: originally called ignore_types, ignore_methods aligns better with the terminology used here and in null-ls/none-ls.

jay-babu / mason-null-ls.nvim

feat: add `ignore_methods` to ignore setup of null-ls source method types #93