Add ID function and other QOL changes.

[sl4shed]

• Added ID function:

  id(val) {
    if (this.elm.id != null) {
      throw Error("The element already has an ID.");
    }
    this.elm.id = val;
    return this;
  }

• Renamed build.js to format.js to reduce confusion
• Added build instructions to readme
• Added documentation for the ID function.
• Added a console.log() to the end of format.js

[datkat21]

LGTM

[datkat21]

For this to be in the next version did you increment the version number yet, if not I'll do that real quick

[datkat21]

OK I'll update the version and push a new release to npm.