Track the number of repos that use the json-schema topic over time

[Relequestual]

We can assess the number of JSON Schema related GitHub repositories over time as a crude metric which will demonstrate the growth in popularity and use of JSON Schema.

We can do this by getting all the repositories with the json-schema topic, and finding out when they were first created.

This will not determine when the first commit of the repository was made, which may be earlier if the repo has commits pushed that are dated before the repository was made on GitHub.

We can plot this data over time.

We cannot directly identify when a topic was assigned to a repository, but we can attempt to identify if the topic was present when the repo was created.
We can make an assumption that the repo was always related to JSON Schema, which feels reasonable.

Here's a list of tasks that should be done in order to close this Issue:

• Store a list of current repos which use the JSON Schema topic and when they were created #4
• Get repo topics and created at date data from search results #11
• Add first commit date to initial repository data #5
• Create weekly job to update the count and list #6
• Create graph of projects on Github that use the json-schema topic over time. #7