refactor: Move SCSS functions and abstract build data retrieval

I've moved the SCSS functions file into the `scripts` directory where I think it makes a bit more
sense. I've also abstracted most of the functionality from it so I can also use it in
`semantic-release`'s preparation step.

scripts/scssFunctions.js

@@ -0,0 +1,7 @@
+const { types } = require('node-sass'); /* eslint-disable-line import/no-extraneous-dependencies */
+
+const getBuildData = require('./getBuildData');
+
+module.exports = {
+  'build-data()': () => types.String(getBuildData(true)),
+};