Refactor build process from Python to JavaScript

[graphemecluster]

• Replace Python build script with JavaScript
  • The 選項 argument of from字頭 now accepts both objects and arrays. (Allowing specifying objects is purely for backward compatibility.) Results are outputted as both array elements and named properties. Closes #77.
• Check coverage during building and testing (Fixes #71)
• Separate type definitions to the dedicated file such that they are recognised when called in a TypeScript file
• Move generated artifacts to a dist directory and make the npm package include only this directory

[syimyuzya]

Also, that "Python" in the VSCode extension recommendations can be removed (and replaced by ESLint).