Slider item does not include a Clear button by default

[nielmdrec]

Describe the bug
For one of our Assessment forms, we are using a slider for Pupil Size.
We noticed that the slider by default does not include a Clear button.

To Reproduce
The sample is below, it consist of 2 questions:

1. Pupil Size (mm)
2. Reaction

For 'Reaction', If you select one of the radio buttons (e.g. No Reaction), you will get a 'CLEAR' button which can be used to clear the answer
However for 'Pupil Size (mm)', if I move the slider across to say 4, there is no 'CLEAR' button.
User is confused and thinks using the 'CLEAR' button on 'Reaction' should also clear the 'Pupil Size' slider.

   {
      "item": [
        {
          "code": [
            {
              "code": "leftEyePupilDiameter",
              "system": "https://fhir.medirecords.com/CodeSystem/mr-parameter-name",
              "display": "Left eye Pupil diameter Manual"
            },
            {
              "code": "1",
              "system": "https://fhir.medirecords.com/CodeSystem/mr-parameter-type",
              "display": "Physical"
            }
          ],
          "text": "Pupil Size (mm)",
          "type": "integer",
          "linkId": "awsLeftPupilSize",
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-itemControl",
              "valueCodeableConcept": {
                "text": "A control where an axis is displayed between the high and low values and the control can be visually manipulated to select a value anywhere on the axis.",
                "coding": [
                  {
                    "code": "slider",
                    "system": "http://hl7.org/fhir/questionnaire-item-control",
                    "display": "Slider"
                  }
                ]
              }
            },
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-sliderStepValue",
              "valueInteger": 1
            },
            {
              "url": "http://hl7.org/fhir/StructureDefinition/minValue",
              "valueInteger": 0
            },
            {
              "url": "http://hl7.org/fhir/StructureDefinition/maxValue",
              "valueInteger": 10
            },
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-observationExtract",
              "valueBoolean": true
            }
          ]
        },
        {
          "code": [
            {
              "code": "leftPupilPupillaryResponse",
              "system": "https://fhir.medirecords.com/CodeSystem/mr-parameter-name",
              "display": "Left pupil Pupillary response"
            },
            {
              "code": "1",
              "system": "https://fhir.medirecords.com/CodeSystem/mr-parameter-type",
              "display": "Physical"
            }
          ],
          "text": "Reaction",
          "type": "choice",
          "linkId": "awsLeftPupilReaction",
          "repeats": false,
          "required": false,
          "extension": [
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-itemControl",
              "valueCodeableConcept": {
                "coding": [
                  {
                    "code": "radio-button",
                    "system": "http://hl7.org/fhir/questionnaire-item-control"
                  }
                ]
              }
            },
            {
              "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-choiceOrientation",
              "valueCode": "vertical"
            },
            {
              "url": "http://hl7.org/fhir/StructureDefinition/minValue",
              "valueInteger": 0
            },
            {
              "url": "http://hl7.org/fhir/StructureDefinition/maxValue",
              "valueInteger": 10
            },
            {
              "url": "http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire-observationExtract",
              "valueBoolean": true
            }
          ],
          "answerValueSet": "#EyeReaction"
        }
      ],
      "text": "Left Pupil",
      "type": "group",
      "linkId": "awsLeftPupil-grp"
    }

Expected behavior
Can we have a 'CLEAR' button for sliders as well.
When pressed, it will clear the value of the slider, as if the question has not been answered.
It should not set it to value '0' because '0' is different to not set.