clean up listeners

code.js

figma.on('selectionchange', () => {
  if (figma.currentPage.selection.length > 1) {
    // assigning values from selection
    calculateAndSendContrast(foregroundColor, foregroundAlpha, backgoundColor)
  }
})
figma.ui.onmessage = msg => {
  if (msg.type === 'swap') {
    // swapping variable values
      calculateAndSendContrast(foregroundColor, foregroundAlpha, backgoundColor)
    }
  }
}