Added slither github action to v8 and minor changes

[niccolopetti]

As referenced in #27 adding static security analysis in the CI pipeline is something desired before releasing v8,
this PR adds that, and a few changes suggested by slither.

I think with this addition, all tests passing and no issues found by slither v8 might be ready to be released (always stating code is unaudited)

[estarriolvetch]

Wow this is awesome!! Thank you :)

I try to find the full slither analysis report, but I cannot find it. Can you point to me where it is?

[niccolopetti]

You're welcome!
On my fork they appear on the Security tab like this, you might need to fork my repo and push something as a test to trigger the action (there has to be a better way but that's the quickest solution that came to my mind rn)

to make slither reports publicly visible something like https://github.com/crytic/slither-action#example-workflow-markdown-report might be implemented, that should create issues in the repo, but it might become a bit messy

[estarriolvetch]

The changes looks good to me. I will merge it into v0.8