feat(search): add local search (#231)

* feat(search): add local search

* docs: add docs for search

src/lib/lunr.segmentit.js

@@ -0,0 +1,8 @@
+import { Segment, useDefault } from 'segmentit';
+
+const segmentit = useDefault(new Segment());
+lunr.segmentit = segmentit;
+lunr.queryHandler = query => {
+    if (/^[\u4e00-\u9fa5]+$/.test(query)) query = lunr.segmentit.doSegment(query).map(seg => '+' + seg.w).join(' ');
+    return query;
+};