Improved documentation for usage in `wasm32-unknown-unknown`

[kylebarron]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

The docs currently say

Support for wasm32-unknown-unknown target

It's possible to build object_store for the wasm32-unknown-unknown target, however the cloud storage features aws, azure, gcp, and http are not supported.

cargo build -p object_store --target wasm32-unknown-unknown 

Am I correct that this assertion is outdated? If the user implements a custom HTTPConnector in wasm32, then one can use aws/azure/gcp/http in wasm32, right?

If so, I think we should improve the documentation here, even if we don't have a full example working in wasm32.

Describe the solution you'd like

Improved documentation

Describe alternatives you've considered

Additional context

[tustvold]

Yes this looks like it got missed