feat: add helix coordinate and related examples/tests

[BQXBQX]

Checklist

• npm test passes

• commit message follows commit guidelines
• documents are updated

Description of change

• Integrated helix coordinate into the core library, enabling G2 to support helix charts.
• Added a helix demo to the official documentation site for showcasing its usage.
• Created and finalized test files for the helix coordinate to ensure functionality and stability.

Fix this

• fixed 螺旋坐标系 #6423

[coveralls]

Pull Request Test Coverage Report for Build 12255378585

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.04%) to 86.704%

---

Files with Coverage Reduction	New Missed Lines	%
src/interaction/tooltip.ts	6	90.97%

Totals
Change from base Build 12211940790:	0.04%
Covered Lines:	10614
Relevant Lines:	11866

---

💛 - Coveralls

[pearmini]

@hustcc 可能需要你帮忙上传一下案例的 preview image？

[hustcc]

@BQXBQX 把 demo 截图发到 issue 评论区，我上传到 oss，给你 url 地址。