Improve error message when unsupported output.hashFunction method is used

[uladzimirdev]

What problem does this feature solve?

I got a cryptic error message:

thread '' panicked at 'not implemented: sha256', crates/rspack_hash/src/lib.rs:22:12

my config:

...
output: {
  ...,
  hashFunction: "sha256"
}

and it's completely valid for webpack, but not for rspack.

What does the proposed API of configuration look like?

It would be nice to print a list of supported methods instead.
As a workaround I used hashFunction: "xxhash64",