Pull out electron-builder config

[irahopkinson]

I've tested this on Windows and Linux production builds.

This should probably be merged after #72 since that moves cSpell settings from .vscode/settings.json to cspell.json and I'll need to rebase and make the same change here.

Resolves #81.

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This change is 

[tjcouch-sil]

Thanks for the great work on this! I like it. We can merge this in before events if you want; like we said, we should all be capable of doing merges well ;)

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @irahopkinson)

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electron-builder.json5 line 1 at r1 (raw file):

/**

I have never heard of json5 files before! I like it :)

[tjcouch-sil]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @irahopkinson)