Support / documentation for Linux users

[jtpio]

Really nice library, thanks for putting that together!

At the moment it looks like the chrome path defaults to the one for Mac when using galata on Linux:

https://github.com/mbektasbbg/galata/blob/91f99885a0be2da7c048d587d9ccf697773b180a/packages/galata/bin/cli.js#L142-L144

Wondering whether it should be the default? Or maybe default to /usr/bin/chromium or which chromium?

Otherwise a small section in the documentation / readme could be enough as a starting point.

[jtpio]

This shouldn't be needed anymore, and fixed by https://github.com/mbektasbbg/galata/pull/11