Add CLI implementation of `merge_match_into_file`

[chrisjsewell]

Once stuff is cached...what do users do next?

As mentioned above, they can inspect the cache for execution statistics etc. But I guess the main use is to create 'merged' notebooks; containing 'up-to-date' text cells from the 'source' file (text or notebook based) and up 'up-to-date' code cells (+ execution specific metadata) from the cached notebook. Currently, this is only available in the API (see merge_match_into_file), but could also me added to the CLI.

Originally posted by @chrisjsewell in https://github.com/ExecutableBookProject/jupyter-cache/issues/16#issuecomment-594958966