Migrate to TypeScript

[whymarrh]

(Edited) We've standardized on using TypeScript for our libraries.

• Add typescript as a development dependencies, and copy tsconfig.json and tsconfig.build.json from the module template.
• Convert existing JavaScript syntax to TypeScript
• Update the build script in package.json to use tsc
• Add a build:clean script
• Add typedoc as development dependencies, copy the build:docs package script from the module template, and copy typedoc.json
• Add ts-node and @types/node as development dependencies
• If this issue is started after Bring linting pipeline in sync with module template #164 is complete, then:
  • Add @metamask/eslint-config-typescript and @typescript-eslint/* packages
  • Ensure that the lint:eslint package script includes ts files
  • Add TypeScript config to .eslintrc.js (again, see the module template)
• If this issue is started after Migrate from Mocha/Chai to Jest #166 is complete, then:
  • Add @types/jest and ts-jest as development dependencies