When printing out the configuration JSON, the Redirector extension
expects regex escapes to be escaped, themselves. So `\` becomes `\\`.
However, Crystal treats these as escaped character also, and each `\`
must additionally be escaped, so a single slash becomes `\\\\`
Instead of providing long detailed instructions for how to configure
the Redirector extension, this provides a single json file that users
can import. I started by making a single file stored in the
`public/assets` directory, but then realized this was a regression since
the instructions were customized to each domain. Instead I can use
Lucky's [data] response to dynamically build the JSON config.
[data]:
https://luckyframework.org/guides/http-and-routing/request-and-response#
handling-responses