[packaging] Include license in PyPi packages (Azure#20193)

* [packaging] Include license in PyPi packages

The MIT license requires that a copy of the license is distributed with
the software. Add the license to the template and also add it to the
manifest file.

Fixes: Azure#20183

Signed-off-by: Major Hayden <major@mhtx.net>
Co-authored-by: Scott Beddall <45376673+scbedd@users.noreply.github.com>
Co-authored-by: Xiang Yan <xiangsjtu@gmail.com>

Author: 3 people

tools/azure-sdk-tools/packaging_tools/templates/LICENSE.txt

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2021 Microsoft
+
+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.

tools/azure-sdk-tools/packaging_tools/templates/MANIFEST.in

@@ -3,4 +3,4 @@ include *.md
 {%- for init_name in init_names %}
 include {{ init_name }}
 {%- endfor %}
-
+include LICENSE.txt