Use multiple columns to display languages options

When the list of available languages becomes too large, having all of
them in one column makes it harder to select them.

What we're trying to do here is to have multiple columns, with each
column containing between 5 and 10 options, so they can all be easily
seen on the screen at the same time.

For that, there are mainly three options: a flex layout, a grid layout
or a multi-column layout.

Since languages are ordered (more or less) alphabetically, the natural
way to display them is showing the first few ones on the first column,
the following ones on the second column, and so on, as opposed to
displaying the first ones on the first row, the following ones on the
secord row, ... AFAIK this can't be accomplished using a flex layout.

I've tried to do so using a grid layout, and failed. The problem here is
that we don't know how many rows we're going to have.

So we're using a multi-column layout. I haven't found a way to guarantee
a minimum height for the content of each column, so in the end we're
using a hack with the `:has` pseudoclass. Note this pseudoclass is only
supported by about 92%-94% of the browsers (including the last few
versions of all major browsers); people using other browsers will still
see all the options on one column, just like people using small screens
do.

app/assets/stylesheets/admin/locales/form.scss

@@ -18,6 +18,19 @@
     padding-top: calc(#{$line-height} / 4);
   }
 
+  .collection-radio-buttons,
+  .collection-check-boxes {
+    column-gap: rem-calc(map-get($grid-column-gutter, medium));
+    column-width: 13rem;
+    max-width: max-content;
+
+    @each $elements in 10, 15, 20, 25, 30 {
+      &:has(label:nth-of-type(#{$elements})) {
+        column-count: calc(#{$elements} / 5);
+      }
+    }
+  }
+
   [type="submit"] {
     @include regular-button;
     display: block;