Upgrade reason-future to Support ReScript 11+

[nicktytarenko]

This PR migrates reason-future from ReasonML to the latest ReScript syntax (v11+). The main objective of this update is to maintain compatibility with ReScript 11+ while preserving the existing functionality and ensuring minimal disruption for current users.

Key Changes

1. README Updated: Reflects the transition from ReasonML to ReScript with updated examples.
2. Tests Adapted: Adjusted existing tests to the new ReScript syntax without altering logic or functionality.
3. File Extensions Renamed: All .re files were converted to .res.
4. Configuration Updated: Migrated bsconfig.json to rescript.json.
5. Core Module Switched: Replaced Belt with @rescript/core for better compatibility with ReScript 11+.
6. Backward Compatibility Maintained: Ensured the library's API and syntax remain consistent to minimize breaking changes for users.
7. Curried vs. Uncurried Functions: Addressed issues where curried functions following uncurried ones are no longer fused in ReScript 11+.

Context

ReScript 11 introduced significant breaking changes, removing support for the legacy Reason syntax (.re). This migration ensures the library remains functional for users on ReScript 11+.

• For ReasonML or ReScript ≤v10 Users: They can continue using [email protected].
• For ReScript 11+ Users: This updated version is necessary to maintain compatibility.

Additional Note

Consider renaming the npm package (e.g., rescript-future) to better reflect its focus on ReScript, following examples like the transition from @glennsl/bs-jest to @glennsl/rescript-jest.