Added testingWithJest, a workshop on Unit Testing with Jest

[beaumoaj]

I have added a workshop on Unit Testing with Jest.
I spoke to Caroline Scherf about this and gave her a quick walkthrough of the workshop. She asked me to create this pull request.

The docs folder contains the instructions in the index.html.

The Javascript files in the project are:

1. day.js - implements some functionality to maintain a list of appointments in a day. The focus of the workshop is the function called makeAppointment down towards the bottom of the file.
2. dayDemo.js - a demo program to show how to use day.js
3. day.test.js - contains three tests that test functionality in day.js. The first one tests that setUpDay correctly sets up a day with all appointment slots available, the second tests that we can make an appointment at 9 am on an empty day, the third tests that we should not be able to make an appointment before the start of the day (at 8 am). The first two tests pass and the third one fails.

The index.html is generated from the README.md using claat (from https://github.com/googlecodelabs/tools/releases). I use the following script to format the markdown into HTML:

#! /bin/sh 

if [ $# -eq 1 ]
then
    STYLE="<\/style><link rel='stylesheet' href='cyf.css'\/>"
    claat export $1

    sed -i "s/<\/style>/$STYLE/g" ./*/index.html
else
    echo "Please enter a markdown file to process"
fi

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[SallyMcGrath]

Thanks so much for this, @beaumoaj ! Just spotted it as I was over here.

Is it possible for you to add some learning objectives to the top? Just 2 would do.
https://common.codeyourfuture.io/common-theme/shortcodes/objectives/