fix: html semantics (base issue)

### &#127919; Aim
- Correctly write the HTML in the sample code
  - To prevent learners from picking up incorrect HTML


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### Todo
- [ ] button type
- [x] img alt
  https://github.com/Ubugeeei/chibivue/pull/215
- [x] input label https://github.com/Ubugeeei/chibivue/issues/212#issuecomment-1874922332
  https://github.com/Ubugeeei/chibivue/pull/216
- [ ] etc...