Add help icon to launcher

[lresende]

Fixes #924

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[lresende]

[lresende]

@ptitzler are we ok for the icon? Also, are we ok on opening the help page on another browser tab?

[ptitzler]

Yes, I like it! Perhaps use "Open documentation" as the label?

[lresende]

[ptitzler]

LGTM. works fine

[ajbozarth]

Overall solid PR, one question on the doc link used, and the icon needed some work. I'll be pushing an update to the icon and a new screenshot right after this.

[ajbozarth]

updated icon to support dark mode

[lresende]

Thanks for the support for dark mode @ajbozarth