feat(env): support multiple environment variables

[CorentinTh]

No description provided.

[Copilot]

Pull Request Overview

This PR adds support for specifying multiple environment variables as fallbacks for a single configuration field. Instead of accepting only a single string for the env property, it now accepts either a string or an array of strings, where the first found environment variable is used.

Key changes:

• Updated type definition to allow string arrays for environment variable names
• Modified environment resolution logic to iterate through multiple variables and use the first found
• Added comprehensive test coverage for the new fallback behavior

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/figue.types.ts	Updated ConfigDefinitionElement type to accept string array for env property
src/figue.ts	Implemented fallback logic to find first available environment variable from array
src/figue.test.ts	Added test cases covering multiple environment variable scenarios
README.md	Added documentation explaining the new environment variable fallback feature

Comments suppressed due to low confidence (1)

README.md:1

• Typo in comment: 'plateform' should be 'platform'.

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