Fix step values for susceptibility slider (#76)

Also fix the readout format to show the value in scientific notation.

geoscilabs/mag/Simulator.py

@@ -769,7 +769,13 @@ def profiledata(Binc, Bdec, Bigrf, depth, susc, comp, irt, Q, rinc, rdec, update
             value=53500
         ),
         depth=widgets.FloatSlider(min=0.0, max=5.0, step=0.05, value=0.5),
-        susc=widgets.FloatSlider(min=0.0, max=800.0, step=5.0, value=1.0),
+        susc=widgets.FloatSlider(
+            min=0.0,
+            max=1.0,
+            step=0.001,
+            value=0.0,
+            readout_format=".2e",
+        ),
         comp=widgets.ToggleButtons(options=["tf", "bx", "by", "bz"]),
         irt=widgets.ToggleButtons(options=["induced", "remanent", "total"]),
         Q=widgets.FloatSlider(min=0.0, max=10.0, step=0.1, value=0.0),