Put it in the Scripts tab of https://github.com/Heath123/pakkit and tick "Enable scripting" BEFORE you join the proxy

script.js

// See the node-minecraft-protocol docs
// When editing your scripts, disable scripting or disconnect so
// you don't get lots of errors.

// Handles packets going from the client to the server
exports.upstreamHandler = function (meta, data, server, client) {
  const breakTime = 8250 // Break time in ms, try changing this
  
  if (meta.name === 'block_dig') {
    if (data.status === 0) {
      console.log('Dig start!', meta)
      const newData = Object.assign({}, data)
      newData.status = 2
      const playerID = global.playerEntityID
      const timeUnit = breakTime / 11
      client.sendPacket('entity_effect',
                        {
                          "entityId": playerID,
                          "effectId": 4,
                          "amplifier": -1,
                          "duration": 20,
                          "hideParticles": 0
                        })
      setTimeout(function() {
        console.log('Stopping anim')
        client.sendPacket('block_break_animation',
                          { entityId: 12, location: data.location, destroyStage: 10 })
        console.log('Sending break!')
        // server.sendPacket(meta, newData)
        server.sendPacket('chat',
                          { message: '/setblock ' + data.location.x + ' ' + data.location.y + ' ' + data.location.z + ' minecraft:air destroy' });
      }, breakTime)
      
      for (i = 0; i < 10; i++) {
        const newI = i
        setTimeout(function() {
          console.log('Sending anim ' + newI)
          client.sendPacket('block_break_animation',
                            { entityId: 123, location: data.location, destroyStage: newI })
        }, (newI + 1) * timeUnit)
      }
    }
  }
  server.sendPacket(meta, data)
}

// Handles packets going from the server to the client
exports.downstreamHandler = function (meta, data, server, client) {
  client.sendPacket(meta, data)
  
  if (meta.name === 'login') {
    global.playerEntityID = data.entityId
    console.log('Set player entity ID:', global.playerEntityID)
  }
  // I can't make cancelling any animations that happened before the effect was applied to work
  // Maybe destroy and replace the block?
  /* else if (meta.name === 'acknowledge_player_digging') {
    console.log('change packet')
    // data.status = 1 // Cancelled digging
    data.successful = false
    // Stop animation
    client.sendPacket('block_break_animation',
                      { entityId: global.playerEntityID, location: data.location, destroyStage: 10 })
  } */
}