[WIP] #33 制御構造を用いたフォーム画面のファイル分割

### !WIP!

- [ ] 分割計画を詰める(以下は仮)
- [ ] index.php
  - [ ] index.php
  - [ ] index.html.php
- [ ] form.php
  - [ ] form.php
  - [ ] form.html.php
- [ ] confirm.php
  - [ ] confirm.php
  - [ ] confirm.html.php
- [ ] done.php
  - [ ] done.php
  - [ ] done.html.php