Add configurable QR code page

README.md

@@ -1,11 +1,52 @@
 # qr
 
-Static webpage intended to be hosted at:
+QR-code webpage intended to be hosted at:
 
 ```text
 192.168.0.226:/var/www/html/qr
 ```
 
+Open QR codes with:
+
+```text
+http://192.168.0.226/qr?what=wifi
+http://192.168.0.226/qr?what=haguest
+```
+
+If `what` is not defined in `what.json`, the page returns `404 Not Found`.
+
+## QR data
+
+Copy the example on the web server:
+
+```bash
+cp what.example.json what.json
+```
+
+Edit `what.json` on the server. It is ignored by git and excluded from deploys because it may contain secrets like Wi-Fi passwords.
+
+Supported entries:
+
+```json
+{
+  "wifi": {
+    "type": "wifi",
+    "label": "Home Wi-Fi",
+    "ssid": "Your WiFi name",
+    "password": "Your WiFi password",
+    "security": "WPA",
+    "hidden": false
+  },
+  "haguest": {
+    "type": "url",
+    "label": "HA Guest",
+    "url": "http://192.168.0.226/haguest"
+  }
+}
+```
+
+The key name, such as `wifi` or `haguest`, is shown in the centre of the QR code.
+
 ## Deploy
 
 ```bash