Improve foundry setup

[janjakubnanista]

In this PR

• Remove dependencies from package.json
  • The forge-std dependency is quite outdated, preferred way of installing this is forge install foundry-rs/forge-std
  • These dependencies are not required in production yet they would end up being installed in users' node_modules (as opposed to devDependencies)
• Add foundry.toml and remove remappings.txt
• Add a basic github workflow to test code once pushed (see the latest run here - I believe I'd need to get approved for this action to run for this PR)

@niran let me know if there are any changes you'd like to me to make, more than happy to oblige!