Update CLI docs

[mtuchi]

Description

Update CLI developer challenge to use workflow execution plan feature, Fixes #339

[daissatou2]

This is a great addition to the CLI page! I know the OS4H team struggled with the concept of running flow jobs locally. Some feedback to consider:

1. Please specify if job id is something that should be made up. Also, should it just be unique to that specific workflow plan file?
2. Can you name the id for the starting job in your example workflow something other than "start"? That confused me a bit.
3. Can we give an example of a realistic workflow plan? Maybe getUsers and then postUsers? With the current docs, I don’t understand how I could format the execution plan so that the output of getUsers could automatically be used as the input of postUsers. Is it not possible to use a file name as the data?
4. What is the difference between “execution plan”, “workflow plan” and workflow execution plan”? I’m seeing all three seemingly referring to the same thing. I think it would be a good idea to use one term.
5. Can you add the text in italics to the docs? “Execution plan is a powerful feature of @openfn/cli that allows you to define a list of jobs and rules for executing them. You can use an Execution Plan to orchestrate the flow of data between systems, and to handle errors and retries in a structured and automated way. For example, if you have two jobs in your workflow (GET users from system A & POST users to system B), you can use your execution plan to automatically run both jobs from start to finish. This imitates the flow and fail trigger patterns on the OpenFn platform where a second job should run after the first one succeeds or fails, respectively, using the data returned from the first job. “
6. After the code snippet on executing the workflow plan (openfn workflow.json -i), include a sentence of what would happen upon execution. For instance “On execution, this workflow plan will first run x job using x data, then run x job using x data”

[taylordowns2000]

@mtuchi , please request a review from me when you've addressed @daissatou2 's changes! excited to get these docs up :-)

[mtuchi]

@daissatou2 thank you for the feedback 👌🏽, i have address you comments and fine turned the language a bit, Also i have added the examples to show how you can run the workflow. Please give it another spin and let me know if it's still confusing or if we can make it better

[daissatou2]

@mtuchi I've added some time on your calendar for us to discuss my feedback.

[daissatou2]

discussed feedback on a call with Mtuchi.

[taylordowns2000]

approved from my end. when aicha approves the content we're good to go

[mtuchi]

discussed feedback on a call with Mtuchi.

@daissatou2 i have incorporated the changes we discussed on our last call, please review and approve this PR if your happy with the changes