Build assets haven't been updated since initial commit

[ockham]

I noticed that none of the files in assets/build have been updated since the initial commit. We should probably remove them (and add to .gitignore?) to avoid confusion.

[ockham]

Oh, they're listed in .gitignore already. Makes sense I guess.

secure-custom-fields/.gitignore

Lines 46 to 50 in 03699ab

	# Assets build directory
	assets/build/**/*.css
	assets/build/**/*.map
	assets/build/**/*.js
	assets/build/**/*.php

[ockham]

Turns out that in git, the directories only contain index.php files. Maybe we should at least exempt those from .gitignore 🤔