Add verification steps to README

[handshake-enthusiast]

Useful comprehensive guides:

• https://www.reddit.com/r/Bitcoin/wiki/verifying_bitcoin_core
• https://bitcoincore.org/en/download/
• https://bitcoin.stackexchange.com/questions/50185/how-to-verify-bitcoin-core-release-signing-keys
• https://www.getmonero.org/resources/user-guides/verification-allos-advanced.html
• https://docs.wasabiwallet.io/using-wasabi/InstallPackage.html
• https://help.ubuntu.com/community/HowToSHA256SUM

Re:

• https://github.com/kyokan/bob-wallet/issues/436
• https://github.com/kyokan/bob-wallet/issues/280
• https://github.com/kyokan/bob-wallet/pull/478#issuecomment-1067161090
• https://github.com/kyokan/bob-wallet/issues/214

This new section could be linked/included into release tags.

[handshake-enthusiast]

@rithvikvibhu the commit contains [ci skip] deliberately. Would be great to skip CI on *.md files changes IMO. I can't trigger the actions manually. I can remove [ci skip] from the commit if we can't proceed without completed checks here, but that would be opposite to what I wanted to achieve. Let me know how we proceed.

[rithvikvibhu]

This project is set up in such a way that those 2 checks must pass to be able to merge PRs, I can't override that.

(Btw this applies to the other PRs also)

[rithvikvibhu]

Thanks for the recent PRs @handshake-enthusiast!