types: add type inference for Story and Variant slots items (fixes #622)

[medfreeman]

infer Story & Variant slots state, based on initState

Description

#622

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• If it's a new feature, provide a convincing reason to add it. Ideally, you should open a suggestion issue first and have it approved before working on it.
• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[codesandbox]

Review or Edit in CodeSandbox

Open the branch in Web Editor • VS Code • Insiders

Open Preview

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.

[netlify]

✅ Deploy Preview for histoire-examples-svelte3 ready!

Name	Link
🔨 Latest commit	5157f6f
🔍 Latest deploy log	https://app.netlify.com/sites/histoire-examples-svelte3/deploys/6541707e310b090008f09d75
😎 Deploy Preview	https://deploy-preview-623--histoire-examples-svelte3.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[netlify]

✅ Deploy Preview for histoire-site ready!

Name	Link
🔨 Latest commit	5157f6f
🔍 Latest deploy log	https://app.netlify.com/sites/histoire-site/deploys/6541707e122709000864c60c
😎 Deploy Preview	https://deploy-preview-623--histoire-site.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[netlify]

✅ Deploy Preview for histoire-examples-vue3 ready!

Name	Link
🔨 Latest commit	5157f6f
🔍 Latest deploy log	https://app.netlify.com/sites/histoire-examples-vue3/deploys/6541707ec9ca3800080b0e32
😎 Deploy Preview	https://deploy-preview-623--histoire-examples-vue3.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[netlify]

✅ Deploy Preview for histoire-controls ready!

Name	Link
🔨 Latest commit	5157f6f
🔍 Latest deploy log	https://app.netlify.com/sites/histoire-controls/deploys/6541707e99c30100085296dc
😎 Deploy Preview	https://deploy-preview-623--histoire-controls.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.