aider: Added regex to extract tokens from name in get_model function.

# Context:
USER: use a regex to check `name` for "-XXk" and set tokens = the number XX
ASSISTANT: To use a regex to check for "-XXk" in the `name` and set `tokens` to the number XX, you can modify the `get_model` function in the `aider/models.py` file. Here's the updated code:

```python
aider/models.py
<<<<<<< ORIGINAL
def get_model(name):
    models = GPT35_models + GPT4_models

    for model in models:
        if model.name == name:
            return model

    tokens = 0

    model = Model(name, tokens)
=======
import re

def get_model(name):
    models = GPT35_models + GPT4_models

    for model in models:
        if model.name == name:
            return model

    match = re.search(r'-([0-9]+)k', name)
    tokens = int(match.group(1)) if match else 0

    model = Model(name, tokens)
>>>>>>> UPDATED
```

This change imports the `re` module and uses the `re.search()` function to find the "-XXk" pattern in the `name`. If the pattern is found, it sets `tokens` to the number XX.

aider/models.py

@@ -20,6 +20,8 @@ GPT35_16k = Model("gpt-3.5-turbo-16k", 16)
 GPT35_models = [GPT35, GPT35_16k]
 
 
+import re
+
 def get_model(name):
     models = GPT35_models + GPT4_models
 
@@ -27,7 +29,8 @@ def get_model(name):
         if model.name == name:
             return model
 
-    tokens = 0
+    match = re.search(r'-([0-9]+)k', name)
+    tokens = int(match.group(1)) if match else 0
 
     model = Model(name, tokens)