Running Prefect Flows doc edits

[orianac]

Adding some requests for more info/additional clarification here:

• make all paths (e.g. runtimes.py) relative for repo so we know exactly where it is
• make a distinction in the set-up of the repo that the only thing a user needs to set-up not contained in the repo is (1) a .yml file and (2) any environment variables. (if we are trending away from using a yml file then specify that as well)
• include a sample yaml file with the exact path where that file is located (with any sensitive information obfuscated) including if the name of the file has to look a certain way
• include a sample environment variable set-up, the file location where those options are specified (with any sensitive information obfuscated) and the name of the file
• in the running a flow section, add a sample parameter file, with each parameter detailed (and whether it's relevant or not for each downscaling method). This might be done easiest by just adding documentation to the generate_valid_json_parameters.ipynb notebook and adding a link to that notebook into the docs here. that way if we change the parameters in the notebook we won't have to remember to update the parameter description in this doc.
• and an explanation of any programmatic tools we have for creating parameter files