feat: add search/filter functionality with result navigation (#114)

[yvng-jie]

This PR implements the search/filter feature requested in #114.

Features

• Search filtering: Filter JSON tree by key and/or value via searchText prop
• Three search modes: searchMode supports 'key', 'value', or 'all'
• Case-sensitive toggle: searchCaseSensitive prop
• Exact/fuzzy matching: searchStrict prop for exact match mode
• Result navigation: nextMatch() / prevMatch() methods exposed via ref, with searchMatchChange event
• Built-in info bar: Optional showSearchResultInfo prop shows match count + ◀▶ buttons
• Text highlighting: Matched text is highlighted with .vjs-highlight class
• Active row highlight: Current navigation target has .is-active-match visual style
• Auto-expand: Matching paths are automatically expanded; collapsed state restored on clear
• Zero-match fallback: Shows original data when no matches found (instead of empty tree)
• Virtual scroll compatible: Works with the existing virtual mode
• Dark theme support: Full dark mode adaptation

New Props

Prop	Type	Default
search	String	''
searchCaseSensitive	Boolean	false
searchStrict	Boolean	false
searchMode	'key' | 'value' | 'all'	'all'

New Events

Event	Payload
searchMatchChange	{ currentIndex, totalCount }

New Expose Methods

Method	Description
nextMatch()	Navigate to next match
prevMatch()	Navigate to previous match
getSearchResultInfo()	Get { currentIndex, totalCount }

[leezng]

Thanks. I have submitted a few ideas.

[yvng-jie]

@leezng Thanks for the review!

1. showSearchResultInfo — I totally agree. The built-in info bar is indeed application-layer UI that doesn't belong in the component. I'll remove the showSearchResultInfo prop along with
   the associated rendering logic and styles. The example (Searchable.vue) already shows how to build this UI at the app layer using the exposed searchMatchChange event and
   nextMatch()/prevMatch() methods, so removing the built-in version keeps the component cleaner.

2. searchText → search — Makes sense, I'll rename the prop to search and update the docs and example accordingly.

I'll push the changes shortly.