Add AccessLint scan engine

[kzhou314]

Closes https://github.com/github/accessibility/issues/10666

Adds AccessLint as a built-in scan engine alongside Axe. Opt in via the scans input, e.g. ["axe", "accesslint"]. With no scans input the default stays axe-only.

[Copilot]

Pull request overview

Adds AccessLint as an additional built-in scan engine in the find GitHub Action, alongside Axe, with selection controlled via the scans input while preserving the default behavior (Axe-only when scans is omitted).

Changes:

• Introduces an AccessLint scan path (runAccesslintScan) and wires it into findForUrl based on a new scans context flag.
• Updates scans parsing logic to treat axe and accesslint as core engines and everything else as plugin names.
• Adds dependencies and test coverage for the new scan engine, plus updates action input documentation.

Show a summary per file

File	Description
.github/actions/find/tests/findForUrl.test.ts	Adds tests ensuring AccessLint runs when selected and composes with Axe/plugins.
.github/actions/find/src/scansContextProvider.ts	Extends scan-selection context to include AccessLint and adjusts plugin detection.
.github/actions/find/src/findForUrl.ts	Adds AccessLint scan execution and maps AccessLint violations into findings.
.github/actions/find/package.json	Adds @accesslint/playwright and @playwright/test dependencies.
.github/actions/find/package-lock.json	Locks new dependencies and updates Playwright resolution.
.github/actions/find/action.yml	Documents new core engine behavior for the scans input.

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• .github/actions/find/package-lock.json: Generated file

• Files reviewed: 5/6 changed files
• Comments generated: 5