[Enhancement] Explain in the README how to change the shape

[LiquidZulu]

Explanation

Currently the README has many examples of the program in use (under "screenshots"), without including the command used to produce the effect pictured. It is not currently clear with cavasik --help or by reading the README how I am supposed to achieve these effects.

Expected Behavior

That I be able to see the commands used to generate featured effects.

Alternative Solutions

Running cavasik --help and looking over the README

Additional Context

No response

Code of Conduct

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