Update YGNodeStyleGetGap to return YGValue (#1753)

Summary:
X-link: https://github.com/facebook/react-native/pull/47973

Gap can be styled using both `points` and `percentages`, but YGNodeStyleGetGap currently returns a float value.

To maintain alignment with the `padding` and `margin` functionalities and allow it to be handled in bridging code, this function has been updated to return YGValue.

Pull Request resolved: https://github.com/facebook/yoga/pull/1753

Reviewed By: joevilches

Differential Revision: D66513236

Pulled By: NickGerleman

fbshipit-source-id: b7110855c037f20780f031f22a945bde4446687d

javascript/src/Node.cpp

@@ -439,8 +439,9 @@ Value Node::getPadding(int edge) const {
       YGNodeStyleGetPadding(m_node, static_cast<YGEdge>(edge)));
 }
 
-float Node::getGap(int gutter) {
-  return YGNodeStyleGetGap(m_node, static_cast<YGGutter>(gutter));
+Value Node::getGap(int gutter) const {
+  return Value::fromYGValue(
+      YGNodeStyleGetGap(m_node, static_cast<YGGutter>(gutter)));
 }
 
 bool Node::isReferenceBaseline() {