Only publish a consumable build to NPM

[dtweedle]

Issue

The SpeechToText repository currently publishes all it's source files directly to the NPM package. NPM is not a revisioning management system and putting the compilation steps into user space defeats the purpose of using npm as a package manager.

There is also the question of added complexity that users face when they try to consume this library, users with stricter typing rules or different compiler versions are going to encounter issues when trying to build.

Proposal

1. Stop publishing source code.
2. Add appropriate build steps
3. Publish only the built files and the needed declarations