Add/Reorganize Requirements

[mmccool]

To be discussed, some possible additional requirements:

• Consistency with existing web programming models (e.g. emulating Workers)
• Support for stateful tasks (as opposed to just FaaS stateless tasks). Actually, it would be useful to have both, since stateless can be more efficient/scalable.
• Support for parallelism in workloads (eg. wasm-parallel proposal, which would be an alternative way to compile parallel workload rather than using multiple workers)

Maybe some more generic ones:

• Scalability
• Performance
• Compatibility
• Resiliency
• Security
• Privacy

[mmccool]

Suggestion: add a set of "high-level requirements" like the second list. Then the detailed requirements can be related to the high-level ones.

Note: both are probably still subject to discussion or at least prioritization.