feat: markdown dialect option, faster search (0.1.1)

- split_markdown/load_markdown: dialect="commonmark"|"python-markdown" so list
  blocks match the HTML structure of the renderer (list after paragraph needs a
  blank line; nesting needs 4 spaces in Python-Markdown)
- SearchEngine caches the searched text per block on load
- regex timeout only for /regex/ terms (words and phrases are linear);
  typical queries over 26k blocks: ~30-140 ms instead of 250-700 ms

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "mdgrep"
-version = "0.1.0"
+version = "0.1.1"
 description = "Boolean full-text search (substrings, phrases, regex, AND/OR/NOT, parentheses) over Markdown and other text blocks, with CLI, Flask API and a JavaScript search widget"
 readme = "README.md"
 license = "MIT"