Make `create-entry` available in themes

[kaitlinbolling]

Description

There is currently an expectation that create-entry will be run within a plugin, as the output uses file paths constructed with plugin_url() (example). Should we consider modifying this to allow developers to run the command within themes? It would need to be a prompt in order to modify the current behavior. Alternately, we could choose a way of getting the URL to the file without relying on plugin/theme specific function calls.