add file writing logic and README update

README.md

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+# RSS to Gemini Converter
+
+A tool to convert RSS feeds to Gemini-compatible text.
+
+## Configuration
+
+The application allows configuring the output directory where converted Gemini files are stored.
+
+- **Environment Variable**: `OUTPUT_DIR`
+- **Command Flag**: `-output`
+
+The default output directory is `./data/gemini`.
+
+## Deployment
+
+- **Production (`zion`)**: Set `OUTPUT_DIR` to `/mnt/hive/shared/gemini`.
+- **Testing (`nyarlathotep`)**: Writing to `/mnt/hive/shared/gemini` is permitted for testing as per user directive.