Update to cabal file instead of hpack package.yaml

[kquick]

To fit with modern (v2) cabal functionality, using a haskell-wasm.cabal file is now more convenient than the package.yaml which requires a separate hpack step.

• Adds a haskell-wasm.cabal file and removes the package.yaml
• Sets upper bounds (next major version) for library dependencies.
• Increases the package version to be greater than the version currently available on hackage.
• Adds some additional warning flags (but does not address revealed warnings in the code).
• Verified buildable with GHC 8.6.5, 8.8.4, and 8.10.4 (as noted in the cabal file).

[SPY]

Thank you!