Search: Add word count and/or time to read option to the search results.

### Impacted plugin

Jetpack

### What

Add an option to display the word count and/or time to read in the search results.

### How

This UI pattern is all over the place, and Search has the data in the index so we can easily return it from the API.

I have definitely had requests for this in the past and I think now that we are starting to support more customization options that it would be an easy feature to try adding.

This could also be an interesting filter option to provide.

For implementation I'd suggest giving the end user control of words per minute and the api only returns the word count. https://wordstotime.com/ has some ok defaults it looks like.

No files or tests are named. Start by locating Jetpack's search-results API and result UI, then verify what indexed word-count data is available; done means an agreed optional result display with configurable reading-time behavior and any agreed filter support.

Written by the indexing model from the issue text.