Return time of the classical Harmonic oscillator (an open TODO from section F)

[abudjum]

Hello,

I tried to solve an open TODO item from the Section F of Physlib.ClassicalMechanics.HarmonicOscillator.Solution which resulted in the following lemma:

Assuming that the initial coordinate and velocity are not simultaneously zero,
the time stamps when the harmonic oscillator returns to its initial coordinate and velocity is
a multiple of its period

[github-actions]

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[jstoobysmith]

This looks good but there are some stray spaces in this which are likely best removed.

[jstoobysmith]

When these are addressed, please could you make a comment with a -awaiting-author to remove said label.

[abudjum]

-awaiting-author

[jstoobysmith]

Great! Many thanks for this first PR - hopefully the first of many :). This now looks good to me. I've approved and will merge shortly!