[WIP] Support Node.js Execution Environment for SSX

[skgbafa]

Description

This adds support for signers in the node execution environment (such as ethers) instead of assuming a browser environment. It also adds an example in node. This addresses #83

Type

• New feature (non-breaking change which adds functionality)

Diligence Checklist

(Please delete options that are not relevant)

• This change requires a documentation update
• I have included unit tests
• I have updated and/or included new integration tests
• I have updated and/or included new end-to-end tests
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

[CLAassistant]

All committers have signed the CLA.

[searchableguy]

Make this configurable perhaps? I would like to use it with other runtime or in other context where we do not have a browser wallet.

[skgbafa]

Closing for now. We are overhauling ssx and adding support for node as part of this. Part of the challenge for this PR has to do this have to do with the wasm bundle we use, it's build for the browser to be able to be consumed by downstream packages. Adding support for node is nontrivial and we are going to do this while we update our wasm and rust bundling process for ssx-rs.