Migration of ParaglideJS to Svelte 5 Runes

Description

This PR updates the ParaglideJS component to use Svelte 5’s new runes system, improving reactivity handling and type safety while maintaining all existing internationalization features.

Changes

Core Updates

• Migrated from reactive declarations ($:) to Svelte 5 runes
• Replaced export let with $props() for better type safety
• Consolidated side effects into a single $effect block
• Maintained slot functionality using standard Svelte slot syntax
• Added comprehensive JSDoc documentation

/claim opral/inlang-paraglide-js#262 Fixes opral/inlang-paraglide-js#262