UI to run reset command from dashboard

[gamebits]

Is your feature request related to a problem? Please describe.
If the number of classic posts to be converted has changed — either because new content has been created, or because NCC has been run — then wp newspack-content-converter reset needs to be run via WP-CLI.

Describe the solution you'd like
Not all users or environments have access to WP-CLI. A way to perform this function from the WordPress dashboard would provide an alternative means to do so.

Describe alternatives you've considered
This request may be made unnecessary by #77.

[gamebits]

The reset command was removed in #129. Closing.