fix: use temp path to save diff image

[shtyr-maxim]

This pull request fixes the error of storing diff images in the project's working directory.

Expected behavior

The difference image is saved in $TMPDIR/... path before copying to reportPath

Actual behavior

The difference image is saved in $PWD/images/... before copying to reportPath

[sipayRT]

hi

thx for your PR. can you, pls, provide an example to reproduce this bug?

[shtyr-maxim]

Hi!

I've created a minimal environment to demonstrate this issue. You can find it here: html-reporter-bug.zip.

After running the npm test command, a new folder called "images" will be created in a project directory.