fix: use type alias instead of interface for Props definitions (#518)

Use `type` instead of `interface` for Props definitions to align with Vue ecosystem best practices. Type aliases are more flexible for union and intersection types, which is the recommended approach in Vue's official documentation and the broader Vue community.

This addresses feedback from GitHub Copilot review on PR #517.

Author: seijikohara

src/components/JsonTreeView.vue

@@ -1,7 +1,7 @@
 <script lang="ts">
 export type ColorScheme = 'light' | 'dark'
 
-export interface Props {
+export type Props = {
   json: string
   rootKey?: string
   maxDepth?: number

src/components/JsonTreeViewItem.vue

@@ -23,7 +23,7 @@ export type ItemData = {
   value?: PrimitiveTypes
 }
 
-export interface Props {
+export type Props = {
   data: ItemData
   maxDepth?: number
   canSelect?: boolean