Add visualization for ktensor

[ghbrown]

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

An example showing parity with TTB for this example:

To do:

• [ ] tests?
• [x] plots within a mode should share ylims by default

(Note: #296 was the original, but it is now closed. My local branches were messed up, so I've fixed that and created this new PR on the appropriate branch. )

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📚 Documentation preview 📚: https://pyttb--301.org.readthedocs.build/en/301/