fix: ts types for headingValue in CalendarHeading and `RangeCalendarHeading components

[n1crack]

🔗 Linked issue

Resolves #638

❓ Type of change

• 🐞 Bug fix (a non-breaking change that fixes an issue)

📚 Description

This pull request addresses a TypeScript typing issue in the CalendarHeading component where headingValue was implicitly typed as any. The solution ensures explicit typing of the slot props, preventing further TypeScript errors and improving type safety.

• Refactored v-slot usage to explicitly declare the type of headingValue as string.
• Added proper TypeScript annotations for slot props, ensuring compatibility with both Vue 3's template syntax and TypeScript's inference.

Btw, I'm using Inertia.js with vite 6.0 with strict types

📸 Screenshots (if appropriate)

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.