bugfix(buildUpdate): export BuildUpdate from watch rather than build

[alan-agius4]

Short description of what this resolves:

Not quite sure if buildUpdate from build is required, but I assume the watch buildUpdate can be used instead as it also offers denouncing. Although in the watch buildUpdate js files are not handled but there is another PR for this #375.

Would be nice if the tasks are wrapped in a module thus you can export the whole module add and consume them something like;

const ionicScripts = require("@ionic/app-scripts");
ionicScripts.watch.buildUpdate(...);

or internally

import { watch } from "./watch";
watch.buildUpdate(...);

import { build } from "./build";
build.buildUpdate(...);
build.runBuildUpdate(...);

The above will also solve the issue that in different module/files the method names are called the same.

Changes proposed in this pull request:

• export BuildUpdate from watch rather than build

Fixes: #366