add custom plugins

lua/custom/plugins/null-ls.lua

@@ -0,0 +1,20 @@
+return {
+  "jose-elias-alvarez/null-ls.nvim",
+  version = "*",
+  dependencies = {
+    "nvim-lua/plenary.nvim",
+  },
+  config = function()
+    local null_ls = require("null-ls")
+    null_ls.setup {
+      sources = {
+        null_ls.builtins.formatting.prettier,
+        null_ls.builtins.formatting.black,
+        null_ls.builtins.formatting.latexindent,
+        null_ls.builtins.formatting.shfmt,
+        null_ls.builtins.code_actions.shellcheck,
+        null_ls.builtins.diagnostics.shellcheck,
+      },
+    }
+  end,
+}