Add section to README

Author: marc0der

README.md

@@ -21,6 +21,66 @@ Please generate me a new rule formatted according to prompts/00-rules-template.m
 
 This ensures consistent structure and keeps rules focused and actionable.
 
+# Using as a Git Submodule
+
+To add this library to your existing project with prompts, you can include it as a git submodule. This creates a `library` subdirectory within your `prompts` folder containing all the rules and templates.
+
+## Setup
+
+1. Navigate to your project's `prompts` directory:
+   ```bash
+   cd prompts
+   ```
+
+2. Add this repository as a submodule named `library`:
+   ```bash
+   git submodule add https://github.com/EqualExperts/llm-rules.git library
+   ```
+
+3. Initialize and update the submodule:
+   ```bash
+   git submodule update --init --recursive
+   ```
+
+4. Commit the submodule addition:
+   ```bash
+   git add .gitmodules library
+   git commit -m "Add llm-rules as library submodule"
+   ```
+
+## Updating the Library
+
+To pull the latest updates from the library:
+
+```bash
+cd prompts/library
+git pull origin main
+cd ..
+git add library
+git commit -m "Update llm-rules library"
+```
+
+## Structure
+
+After setup, your prompts directory will look something like:
+
+```
+prompts/
+├── 01-optional_vendor_validation-oneshot.md
+├── 01-optional_vendor_validation-todo.md
+├── 02-idempotent_post_and_delete-oneshot.md
+└── library/
+    ├── rules/
+    │   ├── domain-driven-design.md
+    │   ├── hexagonal-architecture.md
+    │   ├── kotest.md
+    │   └── kotlin.md
+    └── templates/
+        ├── 00-oneshot_template.md
+        ├── 00-rules-template.md
+        └── 00-todo_template.md
+```
+
 # Prompts
 
-Prompt templates and snippets
+Prompt templates and snippets