chore(BUILD): add `.editorconfig`
fix(BUILD): re-add 'build' directory to gitignore
feat(jade): use jade for creating html templates

* Added jade support, see https://github.com/ngbp/ngbp/pull/63.
* Converted about.tpl.html and index.html to use jade, which will have precedence over existing html templates with same name.
* Updated some README files.