Local variables are one of the things CoffeeScript doesn't compile to
modern JavaScript automatically: it uses `var` instead of `const` or
`let`.
Besides, using `$this = $(this)` is usually done to reference the
current object in another function where the current object is a
different one. Here we were using it with no clear purpose.
Updating it required reorganizing the form so translatable fields are
together.
We also needed to add a `hint` option to the form label and input
methods so the hint wouldn't show up for every language.
Finally, the markdown editor needed to use the same globalize attributes
as inputs, labels and hints, which adds a bit of duplication.
