Huh? It is very concerning to hear this from a founder. It is the same exact level of security as it is executing the same code, just at a different level. Really does not matter what crypto lib you are using if at the end of the day the surrounding code dictates all the security.
Regardless of all this, your open source crypto library doesn't even use the Web Crypto APIs at all, but rather the dreaded js based crypto you are badmouthing (tweetnacl, stablelib)
That's just false. Downloading crypto libraries over the web plagued Javascript crypto for years. We use tweetnacl, stablelib, and webcrypto - and tweetnacl also uses webcrypto!
From your source, chacha20 is used, which is literally not supported by web crypto apis. Again, this makes 0 difference as higher level implementation makes or breaks your crypto.
