Add PyInstaller copyright notice

extra/windows/redist-notices.txt

@@ -1,6 +1,7 @@
 liquidctl executables for Windows bundle the following projects:
 
  - liquidctl
+ - pyinstaller (bootloader)
  - python
  - docopt
  - pyusb (patched)
@@ -46,6 +47,31 @@ along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 ================================================================================
 
+pyinstaller – https://www.pyinstaller.org/
+
+Copyright (c) 2010-2019, PyInstaller Development Team
+Copyright (c) 2005-2009, Giovanni Bajo
+Based on previous work under copyright (c) 2002 McMillan Enterprises, Inc.
+
+
+PyInstaller is licensed under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2 of the License,
+or (at your option) any later version.
+
+
+Bootloader Exception
+--------------------
+
+In addition to the permissions in the GNU General Public License, the
+authors give you unlimited permission to link or embed compiled bootloader
+and related files into combinations with other programs, and to distribute
+those combinations without any restriction coming from the use of those
+files. (The General Public License restrictions do apply in other respects;
+for example, they cover modification of the files, and distribution when
+not linked into a combine executable.)
+
+================================================================================
+
 python – https://python.org
 
 Copyright © 2001-2019 Python Software Foundation; All Rights Reserved