Add a BSD 2 clause license

It's the Pony default so let's provide a default one. It's easy
enough for folks to change.

LICENSE

@@ -0,0 +1,22 @@
+Copyright (C) {COPYRIGHT_YEAR} {COPYRIGHT_HOLDER}
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

USAGE.md

@@ -17,16 +17,15 @@ The contents of this repo are designed to get you up and running with everything
   * Project status
   * How to install using pony-stable
 
-
 You still need to add:
 
-- A License
 - A directory at the root of the project containing your Pony source code
 
 ## It's opinionated
 
 This starter pack is opinionated. We suggest that you review:
 
+- [LICENSE](LICENSE)
 - [CODE_OF_CONDUCT.md](CODE_OF_CONDUCT.md)
 - [CONTRIBUTING.md](CONTRIBUTING.md)
 - [STYLE_GUIDE.md](STYLE_GUIDE.md)
@@ -49,6 +48,8 @@ This repository is templated. You'll want to replace anything in {} with the cor
 - {COC_EMAIL}: email address that Code of Conduct violations should be reported to, for example: `[email protected]`.
 - {PROJECT_DESCRIPTION}: a paragraph describing your project
 - {PROJECT_STATUS}: paragraph or two describing the status of your project. Is it alpha? beta? production-ready? What's left to implement?
+- {COPYRIGHT_YEAR}: if you use the enclosed BSD 2 clause license, you'll need to set the Copyright year.
+- {COPYRIGHT_HOLDER}: if you use the enclosed BSD 2 clause license, you'll need to set the Copyright holder.
 
 ## What you need to create