Add original, unmodified CAPTCHA-SETUP from the webclient repo before modifying (captcha setup is now purely on the HS).

CAPTCHA_SETUP

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+Captcha can be enabled for this web client / home server. This file explains how to do that.
+The captcha mechanism used is Google's ReCaptcha. This requires API keys from Google.
+
+Getting keys
+------------
+Requires a public/private key pair from:
+
+https://developers.google.com/recaptcha/
+
+
+Setting Private ReCaptcha Key
+-----------------------------
+The private key is a config option on the home server config. If it is not 
+visible, you can generate it via --generate-config. Set the following value:
+
+  recaptcha_private_key: YOUR_PRIVATE_KEY
+  
+In addition, you MUST enable captchas via:
+
+  enable_registration_captcha: true
+
+Setting Public ReCaptcha Key
+----------------------------
+The web client will look for the global variable webClientConfig for config 
+options. You should put your ReCaptcha public key there like so:
+
+webClientConfig = {
+    useCaptcha: true,
+    recaptcha_public_key: "YOUR_PUBLIC_KEY"
+};
+
+This should be put in webclient/config.js which is already .gitignored, rather 
+than in the web client source files. You MUST set useCaptcha to true else a
+ReCaptcha widget will not be generated.
+
+Configuring IP used for auth
+----------------------------
+The ReCaptcha API requires that the IP address of the user who solved the
+captcha is sent. If the client is connecting through a proxy or load balancer,
+it may be required to use the X-Forwarded-For (XFF) header instead of the origin
+IP address. This can be configured as an option on the home server like so:
+
+  captcha_ip_origin_is_x_forwarded: true
+
+
+