docs: add docs for flows, start docs for stages

docs/flow/stages/captcha/captcha.md

@@ -0,0 +1,7 @@
+# Captcha stage
+
+This stage adds a form of verification using [Google's ReCaptcha](https://www.google.com/recaptcha/intro/v3.html).
+
+This stage has two required fields. You need a Public and a Private key, both of which you can acquire at https://www.google.com/recaptcha/admin.
+
+![](captcha-admin.png)

docs/flow/stages/dummy/dummy.md

@@ -0,0 +1,5 @@
+# Dummy stage
+
+This stage is used for development, and has no function. It presents the User with a form, that requires a single confirmation.
+
+![](dummy.png)