change co2 frontend to read rel. % (#176)

Author: kevinjin420

teleoperation/basestation_gui/frontend/src/components/SensorData.vue

@@ -20,7 +20,7 @@
           <th>Humidity (%)</th>
           <th>Temp (°C)</th>
           <th>Ozone (ppb)</th>
-          <th>CO2 (ppm)</th>
+          <th>CO2 (Rel. %)</th>
           <th>Pressure (Pa)</th>
         </tr>
       </thead>

teleoperation/basestation_gui/frontend/src/components/SensorModal.vue

@@ -110,7 +110,7 @@ const chartConfigs: readonly ChartConfig[] = [
     datasets: [{ label: 'Ozone', color: '#F9A825', historyIndex: 4 }],
   },
   {
-    title: 'CO₂ (ppm)',
+    title: 'CO₂ (Rel. %)',
     datasets: [{ label: 'CO₂', color: '#8D6E63', historyIndex: 5 }],
   },
   {