Update LICENSE.template with CC-BY + BSD from IPR policy update

Matches whatwg/sg#115.

LICENSE.template

@@ -1,7 +1,10 @@
-Copyright © 2018 WHATWG (Apple, Google, Mozilla, Microsoft).
-This work is licensed under a Creative Commons Attribution 4.0 International License:
+Copyright © 2020 WHATWG (Apple, Google, Mozilla, Microsoft).
+This work is licensed under a Creative Commons Attribution 4.0 International License.
+Alternatively, this work is licensed under a BSD 3-Clause License for incorporation into software.
 
-Attribution 4.0 International
+=======================================================================
+
+Creative Commons Attribution 4.0 International License
 
 =======================================================================
 
@@ -394,3 +397,35 @@ the avoidance of doubt, this paragraph does not form part of the public
 licenses.
 
 Creative Commons may be contacted at creativecommons.org.
+
+=======================================================================
+
+BSD 3-Clause License
+
+=======================================================================
+
+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.
+  3. Neither the name of the copyright holder nor the names of its
+     contributors may be used to endorse or promote products derived
+     from this software without specific prior written permission.
+
+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
+HOLDER 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.