fix: correct the redirection to the official docs in SymbolsTemplate

[YDX-2147483647]

The current <SymbolsTemplate> requires the basePath in metadata to be exactly /docs/.
If not, the redirection will lead to 404 Not Found.
For example, go to https://ydx-typst.netlify.app/reference/symbols/ (basePath === '/') and click Next page, and you'll reach https://typst.app/reference/symbols/sym/ instead of https://typst.app/docs/reference/symbols/sym/.

This PR adds support for other kinds of basePath.

[Copilot]

Pull Request Overview

This PR fixes redirection issues in the SymbolsTemplate component when the basePath is not exactly /docs/. It addresses 404 errors that occur when redirecting to the official Typst documentation from sites with different base paths.

• Adds a new shiftBase utility function that properly handles base path transformation
• Updates SymbolsTemplate to use the new utility instead of hardcoded URL construction
• Refactors BaseTemplate to use the same utility for consistency

Reviewed Changes

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

File	Description
website/src/utils/path.ts	Adds shiftBase function to handle base path transformations
website/src/utils/path.test.ts	Comprehensive test suite for the new shiftBase function
website/src/components/templates/SymbolsTemplate.tsx	Updates redirection logic to use shiftBase utility
website/src/components/templates/BaseTemplate.tsx	Refactors to use shiftBase instead of manual path manipulation

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[3w36zj6]

LGTM