BrowserMode: browser.expect.toMatchScreenshot.beforeComparsion hook

Clear and concise description of the problem

Sometimes you need to make some transformations with images in screenshot tests before comparison.

Now you have only one way - write custom comparator func, but it is difficult way

Suggested solution

allow describe the hook, what called always before image comparator runs

export default defineConfig({
  test: {
    browser: {
      expect: {
        toMatchScreenshot: {
          beforeComparsion: async (pathToReference: string, pathToActual: string): Promise<void> => {...},
          comparators: {
            ...
          },
        },
      },
    },
  },
})

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Start by locating the browser expect.toMatchScreenshot implementation and its comparator configuration entry point described in the issue. Trace how reference and actual image paths reach the comparator, then verify that the proposed beforeComparsion hook runs before comparison and that existing comparator behavior remains intact.