Add copyright owner assertion for all license types (#45)

 Add copyright owner assertion for all license types

---------

Signed-off-by: Facundo Tuesca <facundo.tuesca@trailofbits.com>
Co-authored-by: William Woodruff <william@trailofbits.com>

Author: facutuesca

{{cookiecutter.project_slug}}/README.md

@@ -7,3 +7,45 @@
 <!--- BADGES: END --->
 
 {{ cookiecutter.project_description }}
+
+## License
+{%- if cookiecutter.license == "Apache 2.0" %}
+```
+Copyright {% now 'local', '%Y' %} {{ cookiecutter.author_name }}
+
+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
+    http://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.
+```
+{%- elif cookiecutter.license == "AGPL v3" %}
+```
+Copyright (C) {% now 'local', '%Y' %}  {{ cookiecutter.author_name }}
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as published
+by the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+```
+{%- elif cookiecutter.license == "Proprietary" %}
+```
+Copyright (C) {{ cookiecutter.author_name }}. All rights reserved.
+
+Please contact {{ cookiecutter.author_email }} for licensing terms.
+```
+{%- endif %}