Initialize composer project for WooCommerce Licensed Product Client

- Set up composer.json with package metadata and PSR-4 autoloading
- Add symfony/http-client ^7.0 as HTTP client dependency
- Create project structure (src/, tests/, tmp/)
- Add README.md with project overview
- Add CHANGELOG.md to track version history
- Add .gitignore for vendor and cache files
- Include OpenAPI specification in tmp/openapi.json

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.editorconfig

@@ -0,0 +1,15 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+indent_size = 2