doc(nodes): adding battery to class diagram

linked #63

doc_resources/nodes/class_diagram.puml

@@ -15,6 +15,7 @@ class "Window_status" as win{}
 class "Hygrometer" as hygro{}
 class "Thermometer" as thermo{}
 class "CO2_level" as co2{}
+class "Battery_level" as batt{}
 
 sup o-d- ble
 sup o-u- sens
@@ -22,5 +23,6 @@ sens <|-l- win
 sens <|-u- hygro
 sens <|-u- thermo
 sens <|-r- co2
+sens <|-- batt
 
 @enduml

doc_resources/nodes/sequence_diagram.puml

@@ -10,7 +10,7 @@ sup -> sens : get_value()
 sens --> sup : value
 sup -> ble : advertise(data)
 ble --> sup
-alt CO2 level above 400
+alt CO2 level above 400 OR windows is open
     sup -> sup : sleep 2 minutes
 else else
     sup -> sup : sleep for [last sleep time + 2 minutes]