Add licence for external projects.

README.md

@@ -224,4 +224,12 @@ scheduler.get_profiler().current_run().print_dag(std::cout);
 ...
 ```
 
+## License
+
+The following external libraries are used in this project:
+
+- [catch2](https://github.com/catchorg/Catch2), located in `extern/catch2`
+- [picosha2](https://github.com/okdshin/PicoSHA2), located in `extern/picosha2`
+- The assembly routines from [boost.context](https://www.boost.org/doc/libs/1_73_0/libs/context/doc/html/context/overview.html), located in `lib/context_switcher/asm/fcontext`
+
 

lib/context_switcher/asm/fcontext/LICENSE.txt

+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+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, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.