Script to update environment.prod.ts during build to match npm semver

replace.build.js

/**
 * replace.build.js:  puts the semver from package.json in angular environment.prod.ts
 * see: http://www.bilyachat.com/2017/01/angular-2-build-version.html
 */
var replace = require("replace-in-file");
var package = require("./package.json");
var buildVersion = package.version;
const options = {
  files: "src/environments/environment.prod.ts",
  from: /version: \"(.*)\"/g,
  to: 'version: "' + buildVersion + '"',
  allowEmptyPaths: false
};

try {
  let changedFiles = replace.sync(options);
  if (changedFiles == 0) {
    throw "Please make sure that file '" +
      options.files +
      "' has \"version: ''\"";
  }
  console.log("Build version set: " + buildVersion);
} catch (error) {
  console.error("Error occurred:", error);
  throw error;
}