This pull request adds support for bootstrapping the Reflag browser SDK with pre-fetched flag data, enabling faster initial rendering and improved SSR performance. The changes introduce a new bootstrappedFlags option, update initialization logic to handle bootstrapped clients, and include documentation and tests to cover the new behavior.

Server-side rendering and bootstrapping support:

• Added documentation in README.md on how to use the new bootstrappedFlags option for SSR, including benefits and usage examples.
• Introduced the bootstrappedFlags property to the InitOptions and a new InitOptionsBootstrapped type in client.ts, allowing the client to be initialized with pre-fetched flags. [1] [2]
• Updated ReflagClient and FlagsClient constructors and initialization logic to recognize and properly handle bootstrapped flags, skipping network requests when flags are already provided. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Type and API improvements:

• Exported new types (InitOptionsBootstrapped, FetchedFlags) and updated context types for clarity and better API documentation. [1] [2] [3] [4] [5]

Testing and validation:

• Added tests to verify that bootstrapped clients skip flag fetching and initialization, ensuring correct behavior for SSR use cases.
• Updated existing tests to reflect new error handling when re-initializing an already initialized flags client.

Version bump:

• Bumped the package version to 1.2.0 to reflect the new feature.