Update calc.py to support srain_piezo

[smuliv]

Add support for binary sensor "Rain State Piezo" (srain_piezo)

pull request (home-assistant/core#127004) to update integration in core already made.

This PR fixes or closes issue: #200 & home-assistant/core#125850

[airhead1234]

Works for me, too. Would be great to see the component updated.

[GSzabados]

@joostlek and @pvizeli, the PR for the Ecowitt integration (home-assistant/core#127004) and this PR and its companion (#203) for aioecowitt should have ended up in the What the Heck Month... All three of them has been submitted and none of them has been reviewed, but the one for HA has been prematurely closed, as waiting for the two to be merged to aioecowitt. All of these sitting as idle ducks without any interaction, but has about 4 issues related to them. And the author mentions them every month in one of the issues. Maybe the libraries should have a notification set up for review as the components has it for HA. #whattheheckmonth

[joostlek]

Yes I recently brought this up and I'm trying to get these PRs merged. Please stay tuned.

[GSzabados]

Cool! Thanks! And please excuse me for the comment above, but I don't understand why positive contributions ends up without any interaction for months.
I just updated my Ecowitt Station recently and seeing all the warnings in HA and started to research any issue. But I only see that positive contributions have been closed and neglected.