DALL-E request mech tool

[victorpolisetty]

Proposed changes

Adding DALL-E as a mech tool. To be utilized as a text to image generation tool.

Fixes

N/A

Types of changes

What types of changes does your code introduce? (A breaking change is a fix or feature that would cause existing functionality and APIs to not work as expected.)
Put an x in the box that applies

• Non-breaking fix (non-breaking change which fixes an issue)
• Breaking fix (breaking change which fixes an issue)
• Non-breaking feature (non-breaking change which adds functionality)
• Breaking feature (breaking change which adds functionality)
• Refactor (non-breaking change which changes implementation)
• Messy (mixture of the above - requires explanation!)

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING doc
• I am making a pull request against the main branch (left side). Also you should start your branch off our main.
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works

Further comments

There is currently OpenAI GPT support but no DALL-E support

[0xArdi]

Changes look good @victorpolisetty . Can you add a test like here: https://github.com/valory-xyz/mech/blob/main/tests/test_tools.py#L106

[victorpolisetty]

Added unit test @0xArdi