added scripting docs

docs/faq.md

@@ -9,6 +9,7 @@
 - [Can I change the system prompts that aider uses?](#can-i-change-the-system-prompts-that-aider-uses)
 - [Can I run aider in Google Colab?](#can-i-run-aider-in-google-colab)
 - [How can I run aider locally from source code?](#how-can-i-run-aider-locally-from-source-code)
+- [Can I script aider?](#can-i-script-aider)
 
 ## How does aider use git?
 
@@ -244,3 +245,48 @@ pip install -r requirements.txt
 # Run the local version of Aider:
 python -m aider.main
 ```
+
+# Can I script aider?
+
+You can script aider via the command line or python.
+
+## Command line
+
+Aider takes a `--message` argument, where you can give it a natural language instruction.
+It will do that one thing, apply the edits to the files and then exit.
+So you could do:
+
+```bash
+aider --message "make a script that prints hello" hello.js
+```
+
+Or you can write simple shell scripts to apply the same instruction to many files:
+
+```bash
+for FILE in *.py ; do
+    aider --message "add descriptive docstrings to all the functions" $FILE
+done
+```
+
+## Python
+
+You can also script aider from python:
+
+```python
+from aider.io import InputOutput
+from aider.coders import Coder
+from aider.models import GPT4
+
+# This is a list of files to add to the chat
+fnames = ['foo.py']
+
+# This is the instruction to give to GPT
+message = 'make a script that prints hello world!'
+
+io = InputOutput()
+coder = Coder.create(GPT4, None, io, fnames=fnames)
+
+
+# This will execute that one instruction on those files and then return
+coder.run(with_message=message)
+```