ci(semantic-release): Add package header updating to CI

I've add a script to handle automatically updating bot the CSS and SCSS headers with the relevant
information before publishing. This update is handled as part of `semantic-release`'s preparation
step.

scripts/updatePackageHeader.js

@@ -0,0 +1,29 @@
+#!/usr/bin/env node
+
+const fs = require('fs');
+const path = require('path');
+
+const getBuildData = require('./getBuildData');
+
+const nextVersion = process.argv[2];
+
+if (!nextVersion) {
+  throw new Error('This script requires a version number to be provided');
+}
+
+// Update the SCSS Package Header
+const SCSSFilePath = path.resolve('scss', 'nes.scss');
+let SCSSFile = fs.readFileSync(SCSSFilePath, 'utf8');
+
+SCSSFile = SCSSFile.replace(/^ {2}Version: development/m, `  Version: ${nextVersion}`);
+SCSSFile = SCSSFile.replace(/^#{build-data\(\)}/m, getBuildData());
+
+fs.writeFileSync(SCSSFilePath, SCSSFile, 'utf8');
+
+// Update the SCSS Package Header
+const CSSFilePath = path.resolve('css', 'nes.css');
+let CSSFile = fs.readFileSync(CSSFilePath, 'utf8');
+
+CSSFile = CSSFile.replace(/^ {2}Version: development/m, `  Version: ${nextVersion}`);
+
+fs.writeFileSync(CSSFilePath, CSSFile, 'utf8');