Add calculated fields to pivot tables

[naterush]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

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Expected behavior A clear and concise description of what you expected to happen.

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Desktop (please complete the following information):

• OS: [e.g. Windows 11]
• Browser [e.g. Chrome, Firefox]
• Mito Version [e.g. 0.3.331] (you can find this with pip list)

Additional context Add any other context about the problem here.