Ability to support specific browser

[mmarkelov]

I just think about support this feature, but I haven't got any ideas about clean and simple API.

In this PR my thoughts about it. You can add come configuration to support specific version through jest-playwright.config.js :

module.exports = {
    browser: 'firefox',
    useStandaloneVersion: true,
    ...
}

or with env params: BROWSER=firefox USE_STANDALONE_VERSION=true jest

Also I should think about peerDependencies, should it be replaced with optionalDependencies?

#7

[mxschmitt]

We should probably not move it to peerDependencies, at least these standalone packages. Because otherwise there would be always the warnings during the installation. So for me I would move playwright + standalone versions to optionalDependencies, that should be ok.

[mmarkelov]

I made some changes with this PR. I suppose we must keep it as simple as possible, so I rewrite it to check out package.json for installed playwright package. So you don't need to provide extra params to use specific package