Add visualization for ktensor

[ghbrown]

This PR adds the vis method to ktensor objects. The syntax and options are very similar to the TTB equivalent.

An example showing parity with TTB for this example:

To do:

• [ ] tests?

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📚 Documentation preview 📚: https://pyttb--296.org.readthedocs.build/en/296/

[ghbrown]

I've added default behavior per a conversation with @dmdunla.

[ghbrown]

Closing, as this PR was from the main branch of my fork by mistake. #301 has been opened as the replacement.