range field now correctly takes 0 into account

[ETLaurent]

Summary

Fix range component to make it take into account the 0 value.

What are the specific steps to test this change?

In a piece or widget, add the following field:

rangeRequired: {
        label: 'range',
        type: 'range',
        min: -70,
        max: 70,
        def: 5,
        required: true
}

Edit the piece/widget and set the range value to 0.
Save
Re-open, the range field should be set to 0, not set to the default value.

What kind of change does this PR introduce?

(Check at least one)

• Bug fix
• New feature
• Refactor
• Documentation
• Build-related changes
• Other

Make sure the PR fulfills these requirements:

• It includes a) the existing issue ID being resolved, b) a convincing reason for adding this feature, or c) a clear description of the bug it resolves
• The changelog is updated
• Related documentation has been updated
• Related tests have been updated -> https://github.com/apostrophecms/testbed/pull/313

If adding a new feature without an already open issue, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[linear]

PRO-6866 Range schema field doesn't accept 0 if there is a default value