Option to display concordance numbers

[markfullmer]

Context

This web interface enhancement was conceived by the team during the Spring 2021 summit. Full notes of the meeting can be found at https://docs.google.com/document/d/18F538rmasr101araP_biwB0z2qLKLf39lSmD_hA_Du8/edit#heading=h.vr5p7wmsjb2v

User story

As a teacher, I want the ability to prepend concordance numbering to search results and be able to generate an embed code that will display those results with concordance numbering, so that students can more easily be directed to the specific result we are discussing or is referenced in pedagogical materials.

Acceptance criteria

• The corpus search interface will display a new checkbox toggle titled "Number results" which, when checked, will display incrementing numbers, starting at 1, in the search results.
• When this toggle is checked, if a user subsequently presses "Embed search results," the embed code they are presented will include metadata that will similarly display numbering in the embedded version of the search results.
• By default, concordance numbers will be "off"

[markfullmer]

This has been completed, per writecrow/crow_frontend@cd97f1d