Redo ml5.js track and archive old videos?

A new "image classification" video has been recorded. Here is a to do list, would love help with any of this!

* [x] create page for new image classification video
* [x] create "archive" track (put at the end of the tracks page) for out of date videos that have been replaced, starting with these two: [ml5 image classification 1](https://thecodingtrain.com/tracks/ml5js-beginners-guide/ml5/1-classification/1-image-classification) and [ml5 image classification 2](https://thecodingtrain.com/tracks/ml5js-beginners-guide/ml5/1-classification/2-webcam-classification)
* [ ] Update video descriptions for archived videos to point to new ones
* [ ] update all the ml5 folders to take out the numbering, update all the video description on YouTube with new links
* [ ] create redirects for the old urls

We could skip removing the numbers since they don't actually show up on the website, only in the URLs and maybe it's best to just keep the URLs?