D support
Partially completed D support in here: https://github.com/contextfreecode/w4hi

- [x] `w4 new`: Add new project template
- [ ] `w4 watch`: Add new filename suffix + build/run support
- [ ] `w4 png2src`: Add new language parameter
- [x] Website: Setup documentation
- [x] Website: Translated code snippets for all guide pages