[Slider] Fix small step example

Author: CodySchaaf

packages/material-ui-unstyled/src/SliderUnstyled/SliderUnstyled.js

@@ -304,21 +304,24 @@ const SliderUnstyled = React.forwardRef(function SliderUnstyled(props, ref) {
 
   const handleHiddenInputChange = useEventCallback((event) => {
     const index = Number(event.currentTarget.getAttribute('data-index'));
+    const value = values[index];
+    const marksValues = marks.map((mark) => mark.value);
+    const marksIndex = marksValues.indexOf(value);
 
-    let newValue = parseInt(event.target.value, 10); // TODO this might need to use roundValueToStep instead or something
-
-    newValue = clamp(newValue, min, max); // todo might not be needed since input won't allow it to go outside
+    // TODO this might need to use roundValueToStep instead or something
+    // but since the native input respects the step it doesn't look like we need it
+    let newValue = event.target.valueAsNumber;
+    // TODO add test to make sure when value/step is -4e-8 it still works
 
     if (marks && step == null) {
-      const markValues = marks.map((mark) => mark.value);
-      const currentMarkIndex = markValues.indexOf(values[index]);
-
       newValue =
-        newValue < values[index]
-          ? markValues[currentMarkIndex - 1]
-          : markValues[currentMarkIndex + 1];
+        newValue < value
+          ? marksValues[marksIndex - 1]
+          : marksValues[marksIndex + 1];
     }
 
+    newValue = clamp(newValue, min, max); // todo might not be needed since input won't allow it to go outside
+
     if (range) {
       const previousValue = newValue;
       newValue = setValueIndex({