update: Revise README and add API reference and configuration schema documentation

docs/API_REFERENCE.md

@@ -0,0 +1,50 @@
+# API Reference
+
+This document describes the API and pipeline functions available in `infctl-cli`.
+
+## PipelineStep Structure
+
+Each pipeline step is defined as:
+
+- `name`: Step name (string)
+- `function`: Function to call (string)
+- `params`: List of parameters (array of strings)
+- `retryCount`: Number of retries (integer)
+- `shouldAbort`: Whether to abort on failure (boolean)
+
+## Available Functions
+
+### k8sNamespaceExists
+Checks if a Kubernetes namespace exists.
+- Params: `[namespace]` (string)
+- Returns: error if namespace does not exist
+
+### RunCommand
+Runs a shell command.
+- Params: `[command]` (string)
+- Returns: error if command fails
+
+## Example Pipeline JSON
+
+```
+[
+  {
+    "name": "ensure inf namespace exists",
+    "function": "k8sNamespaceExists",
+    "params": ["infctl"],
+    "retryCount": 0,
+    "shouldAbort": true
+  },
+  {
+    "name": "create php configmap",
+    "function": "RunCommand",
+    "params": ["./scripts/create_php_configmap_ctl.sh"],
+    "retryCount": 0,
+    "shouldAbort": true
+  }
+]
+```
+
+## Notes
+- Only functions defined in the codebase are available for use in pipelines.
+- The API does not expose any HTTP endpoints; all orchestration is via CLI and pipeline JSON.