docs: add Featureflip to the OpenFeature providers

[jhoward321]

Summary

Adds a page for Featureflip under Providers → OpenFeature, alongside the fifteen existing vendor pages, and lists it in that section's meta.json between FeatBit and flagd.

Featureflip's official Node provider, @featureflip/openfeature-node, is a standard @openfeature/server-sdk provider, so it works with @flags-sdk/openfeature as it is. It has been in the OpenFeature ecosystem since 2026-07-17 (open-feature/openfeature.dev#1410), which is after these pages were generated.

About the generated header. The existing pages say they come from pnpm generate-openfeature-providers, which isn't in the public repo. I produced this page from the Tggl page, line for line, so the header, sections, adapter snippet and footer are identical. If you'd rather run the generator, it should give you the same file and this PR can be closed in favour of that. The only differences are the provider name, the provider link (the same URL as our entry in the openfeature.dev dataset) and the setup lines:

import { FeatureflipProvider } from '@featureflip/openfeature-node';

const provider = new FeatureflipProvider({ sdkKey: 'SDK_KEY' });

@featureflip/node is a peer dependency of the provider, which is why it's in the install line.

Disclosure: I work on Featureflip, so this is a self-submission. The PR was prepared with AI assistance.

🤖 Generated with Claude Code

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