feat: Flake | revamp entire flake (#1)

Reviewed-on: #1

dotfiles/nvim/lua/custom/configs/null-ls.lua

@@ -0,0 +1,28 @@
+local augroup = vim.api.nvim_create_augroup("LspFormatting", {})
+local null_ls = require("null-ls")
+
+local opts = {
+  sources = {
+    null_ls.builtins.formatting.black,
+    null_ls.builtins.diagnostics.mypy,
+    null_ls.builtins.diagnostics.ruff,
+  },
+  on_attach = function(client, bufnr)
+    if client.supports_method("textDocument/formatting") then
+      vim.api.nvim_clear_autocmds({
+        group = augroup,
+        buffer = bufnr,
+      })
+
+      vim.api.nvim_create_autocmd("BufWritePre", {
+        group = augroup,
+        buffer = bufnr,
+        callback = function()
+          vim.lsp.buf.format({ bufnr = bufnr })
+        end,
+      })
+    end
+  end,
+}
+
+return opts