Change Voltage chart to use suggested min/max (#1)

The Voltage/Current chart often either shows lines with so little variation that you cannot see changes, or the values go off the top/bottom.

This change allows the chart to adapt dynamically to the values being returned.

src/public/index.html

@@ -2309,14 +2309,14 @@
                             },
                             y: {
                                 min: 0,
-                                max: 30,
+                                suggestedMax: 6,
                                 ticks: {
                                     callback: (label) => `${label}V`,
                                 },
                             },
                             y1: {
-                                min: -500,
+                                suggestedMin: -50,
-                                max: 500,
+                                suggestedMax: 50,
                                 ticks: {
                                     stepSize: 50,
                                     callback: (label) => `${label}mA`,