Document, polyfill, or make friendlier error message when crypto.subtle is undefined

[diehuxx]

Context: https://discord.com/channels/937858703112155166/1130936915038843021/1131012879810842665

Minimal reproduction: https://github.com/tylerami/react-web5-test

We've had a few people run into this on Discord. The root cause is that crypto.subtle is undefined for http origins. The error message is not the most clear. Might be worth documenting in a README or having a friendlier error message.

[angiejones]

more context from @diehuxx for those not on Discord:

The error is coming from crypto.subtle being undefined when using browser environments with insecure origin. localhost is treated similar to https in some browsers, which is why most people wouldn't run into the issue at first. It's only when they do local networking that it becomes relevant.

[frankhinek]

We could also potentially check the isSecureContext and throw a more helpful error message.

 if (globalThis.isSecureContext === false) throw new Error('instructive message')

More info: https://developer.mozilla.org/en-US/docs/Web/API/isSecureContext