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[mention any skills you have]
(endlesstalk.org)
General rules:
Exceptions may be made at the discretion of the mods.
The two dominant style guides in the U.S. (Chicago Manual of Style and the A.P. Stylebook) prescribe no spaces around em dashes. When I do professional writing I default to Chicago, so I learned to eventually omit spaces around em dashes. That's still my main way of distinguishing myself, for now.
Oh it's interesting! In French typography (which I use in English if I don't know this language's rule), there's a normal space between the main text and the dash, and a non-breaking space between the dash and the inclusion. But I may turn to Chicago, now that I know that.
The different style guides are designed for their particular environments. Most American newspapers and magazines follow AP, but most book publishers follow Chicago. Academics in the humanities tend to follow MLA, while academics in the social sciences tend to use APA. Hell, IEEE has a style guide for electrical engineers.
So do whatever you prefer. I tend to use Chicago because that's what I know best, but I have worked professionally in writing and editing publications that followed the Chicago rules.
I would advise against it — I think it looks stupid.