ci(*:skip) Improve automated changelog generation

[charlesbvll]

Issue

Description

Our changelog generation script didn't work automatically with our new PR title format.

Related issues/PRs

N/A

Proposal

Explanation

Use the PR title to categorise the PRs.

Checklist

• Implement proposed change
• Make CI checks pass
• Ping maintainers on Slack (channel #contributions)

Any other comments?

N/A

[danieljanes]

Instead of moving update_changelog to dev, it would be better to keep it in flwr_tool and eventually move flwr_tool into a separate project

[charlesbvll]

Instead of moving update_changelog to dev, it would be better to keep it in flwr_tool and eventually move flwr_tool into a separate project

Shouldn't this be done in a separate PR? I feel like in terms of consistency, it makes more sense to have everything under dev/ (as flwr_tool currently only contains the protoc.py script, whereas dev/ contains all dev scripts similar to the update_changelog.py script)