docs: add runtiem config docs

Signed-off-by: Tuan Anh Tran <[email protected]>

Author: tuananh

RUNTIME_CONFIG.md

@@ -0,0 +1,65 @@
+# Runtime Configuration
+
+## Structure
+
+The configuration is structured as follows:
+
+- **plugins**: An array of plugin configuration objects.
+  - **name** (`string`): Name of the plugin.
+  - **path** (`string`): OCI path or HTTP URL or local path for the plugin.
+  - **runtime_config** (`object`, optional): Plugin-specific runtime configuration. The available fields are:
+    - **skip_tools** (`array[string]`, optional): List of tool names to skip loading at runtime.
+    - **allowed_hosts** (`array[string]`, optional): List of allowed hosts for the plugin (e.g., `["1.1.1.1"]` or `["*"]`).
+    - **allowed_paths** (`array[string]`, optional): List of allowed file system paths.
+    - **env_vars** (`object`, optional): Key-value pairs of environment variables for the plugin.
+    - **memory_limit** (`string`, optional): Memory limit for the plugin (e.g., `"512Mi"`).
+
+## Example (YAML)
+
+```yaml
+plugins:
+  - name: time
+    path: oci://ghcr.io/tuananh/time-plugin:latest
+  - name: myip
+    path: oci://ghcr.io/tuananh/myip-plugin:latest
+    runtime_config:
+      allowed_hosts:
+        - "1.1.1.1"
+      skip_tools:
+        - "debug"
+      env_vars:
+        FOO: "bar"
+      memory_limit: "512Mi"
+```
+
+## Example (JSON)
+
+```json
+{
+  "plugins": [
+    {
+      "name": "time",
+      "path": "oci://ghcr.io/tuananh/time-plugin:latest"
+    },
+    {
+      "name": "myip",
+      "path": "oci://ghcr.io/tuananh/myip-plugin:latest",
+      "runtime_config": {
+        "allowed_hosts": ["1.1.1.1"],
+        "skip_tools": ["debug"],
+        "env_vars": {"FOO": "bar"},
+        "memory_limit": "512Mi"
+      }
+    }
+  ]
+}
+```
+
+## Loading Configuration
+
+Configuration is loaded at runtime from a file with `.json`, `.yaml`, `.yml`, or `.toml` extension. The loader will parse the file according to its extension. If the file does not exist or the format is unsupported, an error will be raised.
+
+## Notes
+
+- Fields marked as `optional` can be omitted.
+- Plugin authors may extend `runtime_config` with additional fields, but only the above are officially recognized.