@vx/text doesn't work with 0 as a number

[ilariaventurini]

Example:

<svg x={0} y={0} width={200} height={200}>
  {/* doesn't work */}
  <Text x={0} y={10} fill="black">
    {0}
  </Text>

  {/* works */}
  <Text x={0} y={10} fill="black">
    0
  </Text>
</svg>

The result is:

<svg x="0" y="0" width="200" height="200">
  <svg x="0" y="0" style="overflow: visible;">
    <text x="0" y="10" fill="black" text-anchor="start">
      <tspan x="0" dy="0em"></tspan> // <-- no child element
    </text>
  </svg>
  <svg x="0" y="0" style="overflow: visible;">
    <text x="0" y="10" fill="black" text-anchor="start">
      <tspan x="0" dy="0em">0</tspan>
    </text>
  </svg>
</svg>

PR #814 should fix this problem.