Add header and comments to npmrc

.npmrc

@@ -1 +1,8 @@
-save-prefix="~"
+; This Source Code Form is subject to the terms of the Mozilla Public
+; License, v. 2.0. If a copy of the MPL was not distributed with this
+; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+; OED does not auto-update minor versions, only patch versions.
+; ~ is the SemVer character specifying this behavior.
+; This directive makes `npm install --save <package>` and similar commands use that instead of "^"
+save-prefix="~"