Expose WiFi signal strength sensor

Update the display to use the renamed sensor ID and refresh
signal readings every 60 seconds.

esphome/energymonitor.yaml

@@ -49,8 +49,7 @@ time:
     servers:
       - de.pool.ntp.org
 
-# Values are maintained in secrets.yaml. Add further peer_allowed_ips entries as
-# needed when the tunnel and Home Assistant network details are available.
+# Values are maintained in secrets.yaml.
 wireguard:
   id: energymonitor_wireguard
   address: !secret energymonitor_wireguard_address
@@ -111,7 +110,6 @@ font:
       - GF_Latin_Kernel
     glyphs: ["äöüÄÖÜß"]
 
-
 globals:
   - id: page_index
     type: int
@@ -123,10 +121,11 @@ globals:
     initial_value: 'false'
 
 sensor:
+  # WiFi signal strength
   - platform: wifi_signal
-    id: wifi_rssi
-    internal: true
-    update_interval: 10s
+    name: "WiFi Signalstärke"
+    id: wifisignal
+    update_interval: 60s
   - platform: homeassistant
     id: grid_power
     entity_id: sensor.netzleistung
@@ -210,8 +209,8 @@ display:
       // A radio-wave Wi-Fi symbol shows RSSI quality; a red slash means disconnected.
       const bool wifi_online = id(wifi_connected);
       int wifi_bars = 1;
-      if (wifi_online && id(wifi_rssi).has_state()) {
-        const float rssi = id(wifi_rssi).state;
+      if (wifi_online && id(wifisignal).has_state()) {
+        const float rssi = id(wifisignal).state;
         wifi_bars = rssi >= -55 ? 4 : rssi >= -67 ? 3 : rssi >= -75 ? 2 : 1;
       }
       const Color wifi_color = wifi_online ? Color(64, 255, 64) : Color(255, 80, 80);