Update main.bicep added gpt-4o-mini (#355)

## Purpose
Address issue 354

## Does this introduce a breaking change?
```
[ ] Yes
[x] No
```

## Pull Request Type
What kind of change does this Pull Request introduce?

```
[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:
```

## How to Test
*  Get the code

```
git clone [repo-address]
cd [repo-name]
```

* Test the code
set the param ```azureOpenAIChatGptModelName``` to gpt-4o-mini in
```infra/main.bicep``` and then run
```
azd up
```

## What to Check
Verify that the implemented model in Azure Open AI is gpt-4o-mini

## Other Information
<!-- Add any other helpful information that may be needed here. -->

infra/main.bicep

@@ -20,7 +20,7 @@ param tags string = ''
 param openAiResourceGroupLocation string
 
 @description('Name of the chat GPT model. Default: gpt-35-turbo')
-@allowed([ 'gpt-35-turbo', 'gpt-4', 'gpt-4o', 'gpt-35-turbo-16k', 'gpt-4-16k' ])
+@allowed([ 'gpt-35-turbo', 'gpt-4', 'gpt-4o', 'gpt-4o-mini', 'gpt-35-turbo-16k', 'gpt-4-16k' ])
 param azureOpenAIChatGptModelName string = 'gpt-35-turbo'
 
 param azureOpenAIChatGptModelVersion string ='0613'