feat(lib): pass file path by position argument

lib/file.ai.yaml

@@ -1,5 +1,5 @@
 ---
-version: 0.2.1
+version: 0.2.2
 type: lib
 description: |-
   the simple text file loader. You can use environment variables in file path, eg, "$HOME/documents/document.md".
@@ -11,6 +11,7 @@ tag:
   - prompt
   - lib
 input:
+  - 0                               # The file path passed by the prompt(position argument)
   - content                         # The file path passed by the prompt
   - onlyContent: {type: "boolean"}  # Only return the content
 output: # the file content