Reasons for making this change

This is a followup to f62cfc4 which broke the build:readme script by removing the Table of Contents section from the README. On subsequent commits this script would fail with:

> toctoc README.md -w

Couldn't find expected TOC pattern: /## Table of Contents([\s\S])+\n---/

This also broke scripts that call build:readme like publish-to-npm and preversion / npm version. The 1.2.1 release must have performed these steps manually.

I don't see any other references to the toctoc dependency so I've removed it.

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
  • I've run npm run cs-format on my branch to conform my code to prettier coding style
• I'm adding a new feature
  • I've updated the playground with an example use of the feature