Allow usage of binaries under a BY-ND license, in addition to AGPL

This should explicitly allow any "no AGPL software allowed" organizations to use HTTP Toolkit freely, at the cost of losing their rights to modify or redistribute it without attribution. My reading of AGPL is that that's allowed anyway, but this provides end users with a clear & explicit option to avoid AGPL entirely for normal use.

Some examples, according to my understanding of these licenses (but IANAL):

* You can download and run HTTP Toolkit binaries locally under either license
* You can redistribute HTTP Toolkit binaries unmodified either under the AGPL constraints, or with attribution under BY-ND
* You can redistribute the HTTP Toolkit source code only under the AGPL constraints.
* You can modify HTTP Toolkit for personal use only under either license.
* You can share modified versions of HTTP Toolkit with others only under the constraints of the AGPL.
* You can build derivative works (e.g. embed HTTP Toolkit in published software/web services) only under the constraints of the AGPL.

This would be an invalid relicensing, as BY-ND adds AGPL-incompatible constraints, but all contributions to this repo were made either by me personally, or by contributors who have signed the CLA (https://cla-assistant.io/httptoolkit/httptoolkit-desktop) granting us the rights to freely relicensing their contributions.

Author: pimterry

README.md

@@ -51,3 +51,12 @@ A few tips:
 * Most distributable build configuration is in under the `build` field in [`package.json`](./package.json).
  * To fully build packages, you may find some platforms complain about that signing certificates are required. You'll probably need to unset fields like `forceCodeSigning` to disable that.
 * In CI, pull requests don't receive secret environment variables, so builds may fail. Confirm that that's what's happening, and if so that's ok - the team will manually build & evaluate PR changes to resolve this.
+
+## License
+
+The HTTP Toolkit desktop application source code is licensed under AGPL-3.0, [as documented in this repo](/LICENSE).
+
+The binary downloads available in this repo or from [httptoolkit.tech](https://httptoolkit.tech) however may be used under one of two licenses: 
+
+* [AGPL-3.0](/LICENSE), for those who want to modify and redistribute them, within the constraints of that license.
+* [Creative Commons Attribution-NoDerivatives 4.0 International License](https://creativecommons.org/licenses/by-nd/4.0/) for those who don't need those rights and want to avoid any concerns about AGPL licensing.