Disable the browser's native spellchecking ability on all form inputs,
except for DText inputs. We do this by setting `spellcheck="false"` on
the <body> tag, and `spellcheck="true"` on DText <input> tags.
This fixes browsers displaying a red wavy underline beneath tags in the
tag search box, among other places. We disable spellchecking globally
because most form inputs, except for DText inputs, aren't meant for
natural English language.
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