message: fix(modifiers/snap): fix offset
  - don't subtract origin from startCoords
  - also add offset to relativeX without target.x
diff: @@ -12,8 +12,8 @@ function start (arg: Interact.SignalArg) {
  if (options.offset === 'startCoords') {
  snapOffset = {
  - x: interaction.coords.start.page.x - origin.x,
  - y: interaction.coords.start.page.y - origin.y,
  + x: interaction.coords.start.page.x,
  + y: interaction.coords.start.page.y,
  }
  }
  else {
  @@ -81,8 +81,8 @@ function set (arg: Interact.SignalArg) {
  if (!target) { continue }
  targets.push({
  - x: utils.is.number(target.x) ? (target.x + offset.x) : relativeX,
  - y: utils.is.number(target.y) ? (target.y + offset.y) : relativeY,
  + x: (utils.is.number(target.x) ? target.x : relativeX) + offset.x,
  + y: (utils.is.number(target.y) ? target.y : relativeY) + offset.y,
  range: utils.is.number(target.range) ? target.range : options.range,
  })
  