Add position vs time plot to Hamiltonian pendulum

**Is your feature request related to a problem? Please describe.**
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This feature request is related to a feature branch that already exist (feature/example_notebooks). I will work on that existing branch to add this small feature.

**Describe the solution you'd like**
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Just a few lines of code in the hamiltonian_pendulum_notebook will do the trick.

**Describe alternatives you've considered**
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N/A

**Additional context**
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N/A