Add traffic flow data

[nrennie]

Thank you for your submission! Please leave this text as-is when you submit, and then check the checklist.

Usability:

• This dataset has not already been used in TidyTuesday.
• The dataset is less than 20MB when saved as a tidy CSV.
• I can imagine at least one data visualization related to this dataset.

Preparation:

• cleaning.R has code to download and clean the dataset, resulting in descriptively-named data.frames.
• I ran saving.R to create csvs and md data dictionaries for each of my data.frames.
• I filled in descriptions for each variable in each of the {dataset}.md files.
• I edited the intro.md file to introduce my dataset.
• I included at least one image for my dataset as a png file.
• I completed the information in meta.yaml, including descriptive alt text for each image.
• I provided information in meta.yaml about how to credit me, and deleted any parts of that block that I do not want you to use.

Closes #769

[jonthegeek]

Just a couple small tweaks. Thanks again!

[jonthegeek]

/assign traffic-flow 2024-12-03

[jonthegeek]

Looks good. Thanks!