Add initial project structure with README, Cargo configuration, and main logic

- Create .gitignore to exclude target and output directories
- Initialize Cargo.toml with project metadata and dependencies
- Add README.md with project description, features, installation, and usage instructions
- Implement main.rs for extracting blog posts from HTML files and exporting to JSON and text formats

Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "blog-extractor"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+scraper = "0.25.0"
+serde = { version = "1.0.228", features = ["derive"] }
+serde_json = "1.0.145"