Add missing license header

lua/config/notify.lua

@@ -1,2 +1,18 @@
+--[[
+    Copyright 2023 Oscar Wallberg
+
+    Licensed under the Apache License, Version 2.0 (the "License");
+    you may not use this file except in compliance with the License.
+    You may obtain a copy of the License at
+
+        https://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
+]]
+
 vim.notify = require("notify")
 require("telescope").load_extension("notify")