shared: add missing `getPlatform()` type-check helper and unit tests

[ShantKhatri]

Summary

Extend packages/shared/src/platforms.ts with a helper function to safely test platform presence and add corresponding tests.

Tasks

• add export function isSupportedPlatform(id: string): boolean to platforms.ts using PLATFORMS[id] !== undefined.
• add tests in packages/shared/src/__tests__/platforms.test.ts for existing/unknown platform IDs.

Acceptance Criteria

• helper is exported and tests pass.
• this is low-risk contribution and improves API discoverability.

[amritbej]

Hello @ShantKhatri,

I would like to work on this issue. I can add the "isSupportedPlatform(id: string): boolean" helper in "packages/shared/src/platforms.ts" and include unit tests for both valid and invalid platform IDs in "packages/shared/src/tests/platforms.test.ts".

I’ll ensure the helper is properly exported and that all related tests pass successfully.

Please assign this issue to me. Thank you!

[Harxhit]

@amritbej I have assigned this issue to you.

[Satvik-art-creator]

@Harxhit I would like to work on this