chore(deps): make express an optional peer dependency

[benmccann]

Summary

closes #2814

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @benmccann to sign the Salesforce Inc. Contributor License Agreement.

[benmccann]

I have signed the CLA

[WilliamBergamin]

Hi @benmccann thanks for bringing this up 💯

We need to make express a required peer dependency, making it an optional peer dependency might be considered a breaking change for some users, once resolved we should be good to merge

[WilliamBergamin]

Since express is currently a dependency we can't make it an "optional" peerDependency since some users may be relying on it to transitively import express in their projects, this would cause a breaking change

Removing this section would make express a required peer-dependency (non-breaking change), this will allow users to explicitly exclude it from their projects with npm install --omit peer

[benmccann]

I guess we need to wait for the next major to merge this. The stale bot is trying to close the associated issue. Maybe it could be tagged as the next major to keep it open?