Test harness is outdated

[mcmire]

To achieve consistency with our other libraries, we should

• Convert the tests in this repo from Tape to Jest (also using TypeScript instead of JavaScript)
• Add @types/jest, jest, jest-it-up, and ts-jest as dependencies (use same versions as in module template)
• Update the test package script to run jest && jest-it-up instead of tape (copy from the module template)
• Add a test:watch package script (copy from the module template)