Add GPL Cooperation Commitment (PHPMailer#1644)

COMMITMENT

@@ -0,0 +1,46 @@
+GPL Cooperation Commitment
+Version 1.0
+
+Before filing or continuing to prosecute any legal proceeding or claim
+(other than a Defensive Action) arising from termination of a Covered
+License, we commit to extend to the person or entity ('you') accused
+of violating the Covered License the following provisions regarding
+cure and reinstatement, taken from GPL version 3. As used here, the
+term 'this License' refers to the specific Covered License being
+enforced.
+
+    However, if you cease all violation of this License, then your
+    license from a particular copyright holder is reinstated (a)
+    provisionally, unless and until the copyright holder explicitly
+    and finally terminates your license, and (b) permanently, if the
+    copyright holder fails to notify you of the violation by some
+    reasonable means prior to 60 days after the cessation.
+
+    Moreover, your license from a particular copyright holder is
+    reinstated permanently if the copyright holder notifies you of the
+    violation by some reasonable means, this is the first time you
+    have received notice of violation of this License (for any work)
+    from that copyright holder, and you cure the violation prior to 30
+    days after your receipt of the notice.
+
+We intend this Commitment to be irrevocable, and binding and
+enforceable against us and assignees of or successors to our
+copyrights.
+
+Definitions
+
+'Covered License' means the GNU General Public License, version 2
+(GPLv2), the GNU Lesser General Public License, version 2.1
+(LGPLv2.1), or the GNU Library General Public License, version 2
+(LGPLv2), all as published by the Free Software Foundation.
+
+'Defensive Action' means a legal proceeding or claim that We bring
+against you in response to a prior proceeding or claim initiated by
+you or your affiliate.
+
+'We' means each contributor to this repository as of the date of
+inclusion of this file, including subsidiaries of a corporate
+contributor.
+
+This work is available under a Creative Commons Attribution-ShareAlike
+4.0 International license (https://creativecommons.org/licenses/by-sa/4.0/).

README.md

@@ -34,7 +34,7 @@ Formatting email correctly is surprisingly difficult. There are myriad overlappi
 The PHP `mail()` function usually sends via a local mail server, typically fronted by a `sendmail` binary on Linux, BSD and OS X platforms, however, Windows usually doesn't include a local mail server; PHPMailer's integrated SMTP implementation allows email sending on Windows platforms without a local mail server.
 
 ## License
-This software is distributed under the [LGPL 2.1](http://www.gnu.org/licenses/lgpl-2.1.html) license. Please read LICENSE for information on the software availability and distribution.
+This software is distributed under the [LGPL 2.1](http://www.gnu.org/licenses/lgpl-2.1.html) license, along with the [GPL Cooperation Commitment](https://gplcc.github.io/gplcc/). Please read LICENSE for information on the software availability and distribution.
 
 ## Installation & loading
 PHPMailer is available on [Packagist](https://packagist.org/packages/phpmailer/phpmailer) (using semantic versioning), and installation via [Composer](https://getcomposer.org) is the recommended way to install PHPMailer. Just add this line to your `composer.json` file: