Add changelog entry step to contribution flow

[blakeNaccarato]

• https://github.com/blakeNaccarato/copier-python/pull/424

• 425

• 426

Discussed in https://github.com/blakeNaccarato/copier-python/discussions/422

^{Originally posted by **blakeNaccarato** June 25, 2024} ### Please check for similar discussions first - [X] I [searched](https://github.com/blakeNaccarato/copier-python/discussions/categories/ideas-for-infrastructure) and couldn't find an appropriate discussion to participate in instead. ### Description Add this to the pull request template checklist, contributing documentation, and `.vscode/tasks.json`