[WIP] Add parser build warning

[Aerijo]

This is an eye-catching block that shouts about parsers needing to be prebuilt.

I still need to make / write the gist about how to set it up. Alternatively, and appendix in the flight manual might be better.

Either way, I don't want to add any more to the section here. The steps, with enough templates and images, would be considerably long.

CI fails because the link is blank currently. Change in action:

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Closes https://github.com/atom/atom/issues/17971