feat: improve security

[Cyber-Syntax]

• Verify checksum_file via digest verification provided from github_api to prevent tampered checksum_file attacks. Most of the new apps provide digest for their appimage and checksum_file on github api.
• remove sha1/md5 support "“We recommend that anyone relying on SHA-1 for security migrate to SHA-2 or SHA-3 as soon as possible.” —Chris Celi, NIST computer scientist" + "MD5 is a deprecated hash algorithm that has practical known collision attacks. You are strongly discouraged from using it. Existing applications should strongly consider moving away." from https://cryptography.io/en/latest/hazmat/primitives/cryptographic-hashes/#md5