add optional arguments to make sure generate() works without tokenizer being defined

[JackCai1206]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #483

Type of change

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• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] This change requires a documentation update

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Checklist:

• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] I have not rewritten tests relating to key interfaces which would affect backward compatibility

[bryce13950]

@JackCai1206 Do you have a moment to pop in and resolve these errors https://github.com/neelnanda-io/TransformerLens/actions/runs/8654322622/job/23731321640?pr=488?