Update PR template

[illian01]

Description

Please include a summary of this pull request in English. If it closes an issue, please mention it here.

Closes: ~

We recommend to link at least one existing issue for PR. Before your create a PR, please check if there is an issue for this change.

Change(s)

• Add comments on PR template

Code Formatting

If you PR to either master or dev branch, you should follow the code linting process. Please check your code with lint_check.sh in ./scripts directory.
For more information, please read the contribution guide in CONTRIBUTING.md.

Changelog

If your PR is granted to dev branch, codeowner will add a brief summary of the change to the Upcoming Release section of the CHANGELOG.md file including a link to the PR (formatted in markdown) and a link to your github profile.

For example,

- Added a new feature by `@myusername` in [PR 2023](https://github.com/Nota-NetsPresso/netspresso-trainer/pull/2023)