💡Add .sha256 checksum files for each asset

**Describe the feature you'd like**
For each asset in a release eg: `cloudflared-linux-arm64` there should be an associated checksum file eg: `cloudflared-linux-arm64.sha256` that contains the checksum. This would make the process of validating the checksums much easier instead of having to parse the `body` of the release eg `curl -s https://api.github.com/repos/cloudflare/cloudflared/releases/tags/2025.2.0 | jq -r .body` and then iterate through the list.

Simply downloading `cloudflared-linux-arm64` and `cloudflared-linux-arm64.sha256` and then comparing the output of `shasum -256 cloudflared-linux-arm64` to the value inside of `cloudflared-linux-arm64.sha256` would be a more straightforward process for doing this programatically.