Build a Flagsmith Adapter for Flags SDK

Vercel recently launched Flags SDK, an open-source feature flagging framework ([Changelog](https://vercel.com/changelog/npm-i-flags)). Our competitors like LaunchDarkly, Statsig, and Optimizely already have integrations with Flags SDK. By building a Flagsmith Adapter, we ensure Flagsmith is featured alongside them, reinforcing our position in the feature flagging space and ensuring early adopters have Flagsmith as an option, driving adoption.

- Develop a Flagsmith Adapter for Flags SDK using the [Flagsmith JS Client](https://github.com/Flagsmith/flagsmith-js-client).
- Ensure compatibility with Flags SDK’s adapter model, replacing the decide and origin parts of a flag declaration.
- Ensure compatibility with [Flags Explorer](https://vercel.com/docs/feature-flags/using-vercel-toolbar). It allows users to use Vercel Toolbar to view, override, and share feature flag configurations directly from their browser without affecting other users or automated tests.