Add details of process for disposal of LiPo batteries

[PeterJCLaw]

We should document what we do with batteries which are no longer usable.
Once added we should cross link with https://github.com/srobo/recurring-tasks/blob/13764da5b5cb3bef35b0c9b0b57a0c68aa050554/comp/safety/sad-battery-management.yaml

[richardbarlow]

I'd be interested to know the outcome of this. I have 74 old SR batteries that I've been trying to return since 2020. I have emailed info@ with the details and @Scarzy tells me that this has been forwarded onto the kit team.