Write CLI for build and create projects
Commands:
- [x] `create`: Creates a new project with `happyx`.
  Generated project structure may be:
  ```
  project/
  ├─ public/
  ├─ .gitignore
  ├─ README.md
  ├─ src/
     ├─ app.nim
  ```
- [x] `dev`: Run hotreloader server for `SPA` project
- [x] `build`: Build standalone SPA
