Add FriendlyCaptcha

replace/google-recaptcha.md

@@ -15,3 +15,13 @@ Securimage is an open-source free PHP CAPTCHA script for generating complex imag
   - **Source code**: [GitHub](https://github.com/dapphp/securimage)
   - **License**: [BSD 2-Clause "Simplified"](https://github.com/dapphp/securimage/blob/master/LICENSE.txt)
 {% endinfobox %}
+
+## FriendlyCaptcha
+
+FriendlyCaptcha is a proof-of-work based CAPTCHA in which the user's device does all the work.
+
+{% infobox %}
+ - **Website**: friendlycaptcha.com
+ - **Source code**: [GitHub](https://github.com/gzuidhof/friendly-challenge)
+ - **License**: *None*
+{% endinfobox %}