added 42 coding stuff

lua/plugins/42header.lua

@@ -0,0 +1,15 @@
+return {
+  "Diogo-ss/42-header.nvim",
+  cmd = { "Stdheader" },
+  keys = { "<F1>" },
+  opts = {
+    default_map = true, -- Default mapping <F1> in normal mode.
+    auto_update = true, -- Update header when saving.
+    user = "mbonnard", -- Your user.
+    mail = "mbonnard@student.42angouleme.fr", -- Your mail.
+    -- add other options.
+  },
+  config = function(_, opts)
+    require("42header").setup(opts)
+  end,
+}