(feature) Implement Open-feature web provider.

[thomaspoignant]

Requirements

Now that the Open Feature web SDK is available it could be great to implement a client provider for GO Feature Flag for the web SDK.

To continue to support community initiatives we will place the provider in the js-sdk-contrib repository.

Please create a new folder called go-feature-flag-web and ping @thomaspoignant for review in the pull request on the contrib repo.

[thomaspoignant]

This diagram represents the life cycle we want to introduce:

sequenceDiagram
    participant sdk as Open Feature SDK
    participant provider as GO Feature Flag provider
    participant proxy as GO Feature Flag relay proxy
    sdk->>provider: intialize
    
    provider->>proxy: Call getAllFlags() API
    proxy-->>provider: all flags
    
    provider->>proxy: Start websocket hand check
    proxy-->>provider: Websocket session open
    provider-->>sdk: end of initialization
    
    Note over sdk,proxy: After this moment we can call the SDK to be able to retrieve flag values

    loop Every X minutes
        provider->>proxy: Call getAllFlags() API
        proxy-->>provider: all flags
    end

    alt flag changes
        proxy-->>provider: (websocket) notify flag change
        provider->>proxy: Call getAllFlags() API
        proxy-->>provider: all flags
    end
    
    sdk->>provider: getBool()
    provider->>provider: reading flag value in cache
    provider-->>sdk: usage cache value to return result

Loading

In case of disconnection of the WebSocket, we should be able to reconnect using a random exponential backoff algorithm to avoid a pick in a number of connections at one.

[thomaspoignant]

A first version of the provider is in review in the open-feature contrib repository: open-feature/js-sdk-contrib#474.

It requires a fix in the web-sdk to work perfectly, I have open this issue open-feature/js-sdk#488.