Add WP-CLI commands

[crstauf]

It would save so much time if the tools were available via WP-CLI. Recently had to reset indexable tables across a network of 70+ sites, and was painstaking to login to each site and perform the operation, especially knowing that it would've only been a few minutes if there were CLI commands.

[jeroenrotty]

Hey @crstauf,

Please know that our wp yoast index command has a --network parameter. See https://developer.yoast.com/features/wp-cli/reindex-indexables/