[ext.screenshot] Select browser to take screenshots.

[attakei]

Overview

In v2.7.1, sphinx_revealjs.ext.screenshot uses Google Chrome from Playwright to take screenshots (ref).

But any presantation authors do not use always Google Chrome as default browser.
Playwright (deps of sphinx_revealjs.ext.screenshot) supports firefox and webkit,
it may be can used these instead of Google Chrome by users.

Example

conf.py

revaljs_screenshot_browser = "chromium"  # chromium, firefox or webkit (playwright supported browsers)