Add Fourier-Series Method

[conema]

Hello !

I was trying to use this package in one of my projects, but I found the existing methods to be too slow. In the literature[1], I found this other method, named "The Fourier-Series Method for Laplace Transforms", which seems to be pretty simple and fast (at least in my use case).
I don't usually play around with inverse Laplace transformations, so I cannot compare this method with the others, but I thought that it could be interesting to add it to the package.

Let me know what you think about it

[1] https://link.springer.com/chapter/10.1007/978-1-4757-4828-4_8

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[conema]

Just to be sure that somebody is pinged with the PR @jlapeyre

[jlapeyre]

Thanks! I didn't see this before, or forgot. I'll look at it.