added import check from astropy for LombScargle

[LucaCerina]

I've noticed that Astropy 6.0.0 changed part of the API so now LombScargle periodogram fails to import (see https://docs.astropy.org/en/v6.0.0/changelog.html)

I've included an import check to be sure it doesn't crash.
I don't know if astropy 3.0.4 is a hard requirement, but if it's just for LombScargle it can be probably increased to the latest version.

[alexsanjoseph]

This looks good to me.

[Saskia-K]

I was just about to propose the same. Thanks @LucaCerina ! Hoping this gets merged soon.

[LucaCerina]

@robinchampseix what is the status of the project? Does it need helps in terms of maintenance?

[LucaBia]

This works for me too! Thank you @LucaCerina

[masud1901]

I was about to say this.

[MatthewKrinn1]

Without this line, my code will not compile and actually import hrv-analysis. Because of this, I can't use it in my product.