* Make throwOnError=true the new default
* Handle JS errors as part of the RPC request/response flow
* Return a new Result type with .Err on it
This enables constructs on the form:
```handlebars
{{ with transform.ToMath "c = \\foo{a^2 + b^2}" }}
{{ with .Err }}
{{ warnf "error: %s" . }}
{{ else }}
{{ . }}
{{ end }}
{{ end }}
```
Note that the new `Result` type behaves like `template.HTML` (or a string if needed) when printed, but it will panic if in a error state.
Closes#12748
While very useful on its own (and combined with the passthrough render hooks), this also serves as a proof of concept of using WASI (WebAssembly System Interface) modules in Hugo.
This will be marked _experimental_ in the documentation. Not because it will be removed or changed in a dramatic way, but we need to think a little more how to best set up/configure similar services, define where these WASM files gets stored, maybe we can allow user provided WASM files plugins via Hugo Modules mounts etc.
See these issues for more context:
* https://github.com/gohugoio/hugo/issues/12736
* https://github.com/gohugoio/hugo/issues/12737
See #11927
