Add license file

Author: mhartl

LICENSE.md

@@ -0,0 +1,33 @@
+All source code in the [Ruby on Rails Tutorial](https://www.railstutorial.org/) is available jointly under the MIT License and the Beerware License. (This means you can use one or the other or both.)
+
+```
+The MIT License
+
+Copyright (c) 2022 Michael Hartl
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+```
+
+```
+THE BEERWARE LICENSE (Revision 42)
+
+Michael Hartl wrote this code. As long as you retain this notice you can do
+whatever you want with this stuff. If we meet some day, and you think this
+stuff is worth it, you can buy me a beer in return.
+```