Adding support for Chromium in the default Unix binaries

[offray]

Hi and thanks for this project. I have been using it for the MiniDocs package, which extends documentation capabilities of Lepiter with light formats, including Mardeep preview and exportation.

A single line could be added to UnixChromePlatform class >>defaultExecutableLocations, so Pharo-Chrome would detect installations of Chromium in Unix, for those of us that prefer it over Chrome.

Thanks.

[astares]

@offray Sure - if you need it quick just send a PR

[offray]

@astares I'm not in any particular rush, so I will wait. Thought I will be happy of learning about Git based workflows, particularly on Pharo/GToolkit.

[astares]

On my system I used snap now to install. So we have to additionally add " '/snap/bin/chromium'" as a possible path

[astares]

@offray Fixed