Add license file

[MisterAwesome23]

Arduino_CRC32.cpp contains the following-

"Copyright (c) 2020 Arduino. All rights reserved.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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 Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA"

Kindly check if this license template is compliance with the above mentioned.
I've chosen GNU Lesser General Public License version 2.1 as mentioned in the cpp file, still if any specifics needs to be added / changed kindly review.

[aentinger]

Hi 👋 Why not provide the latest version of the LGPL? https://www.gnu.org/licenses/lgpl-3.0.txt

[MisterAwesome23]

Hey :)
I tried putting the very version mentioned in the license text. Though it also says-

version 2.1 of the License, or (at your option) any later version.

Do you want me to use the latest 3.0 one instead then?

[aentinger]

Yes please.

[MisterAwesome23]

I've updated the license to the latest- GNU LGPL 3.0

[aentinger]

Thank you 👍