feat: enable support for volcengine

[Blankll]

This pull request adds first-class support for Volcengine veFaaS (函数服务) as a serverless provider for Express and Koa applications. It introduces a new provider implementation, updates the type system to include Volcengine, enhances provider detection logic, and extends documentation and test fixtures accordingly.

Volcengine veFaaS Support

• Added a new VolcengineProvider class to handle event normalization, response formatting, and provider detection for Volcengine veFaaS. (src/providers/volcengine.ts)
• Registered the new provider in the provider registry and exported it for external use. (src/providers/index.ts) [1] [2]
• Introduced Volcengine-specific event, context, and response types. (src/types/volcengine.ts, src/types/index.ts) [1] [2] [3] [4]

Documentation Updates

• Updated the README.md to document Volcengine support, including provider tables, detection fields, usage examples, and API reference. [1] [2] [3] [4]

Provider Detection Improvements

• Refined detection logic for Aliyun and added detection logic for Volcengine to avoid misidentification between providers. (src/providers/aliyun.ts, src/providers/volcengine.ts) [1] [2]

Test Fixtures

• Added Volcengine context and event fixtures for testing. (tests/fixtures/volcengineContext.ts)

Tencent Test Fixture and Test Improvements

• Updated Tencent test fixtures and added comprehensive tests for Express 5.x and Koa 2.x integrations with Tencent SCF. (tests/fixtures/tencentContext.ts, tests/index-tencent-express-5x.spec.test.ts, tests/index-tencent-koa-2x.spec.test.ts) [1] [2] [3] [4]

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.17%. Comparing base (b4c04c0) to head (d0b04b9).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #13      +/-   ##
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+ Coverage   92.59%   93.17%   +0.58%     
==========================================
  Files          12       13       +1     
  Lines         270      293      +23     
  Branches       53       59       +6     
==========================================
+ Hits          250      273      +23     
  Misses         15       15              
  Partials        5        5              

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