chore: add CHANGELOG.md file to ProgressStepper alpha component

[lilbitner]

Purpose of PR

Similar to this PR, since ProgressStepper is an alpha package, it does not have a CHANGELOG.md, yet the prelease script tries to access it, so I have added it here.

This should resolve the build failure in the most recent commit to main.

PR Checklist

• [X] I have read the relevant readme.md file(s)
• [X] All commits follow our Git commit message convention
• [X] Tests are added/updated/not required
• [X] Tests are passing
• [X] Storybook stories are added/updated/not required
• [X] Usage notes are added/updated/not required
• [X] Has been tested based on Contentful's browser support
• [X] Doesn't contain any sensitive information

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 8fcb5bf0b96c04337e0c5cf0cf735e71052b2db3

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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Name	Status	Preview	Updated (UTC)
forma-36	✅ Ready (Inspect)	Visit Preview	Jul 10, 2024 10:34pm

[github-actions[bot]]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
CommonJS	135.98 KB (0%)	2.8 s (0%)	115 ms (+33.9% 🔺)	2.9 s
Module	132.24 KB (0%)	2.7 s (0%)	104 ms (+16.37% 🔺)	2.8 s