use ESM module syntax & minor cleanups

The biggest change here is moving various element classes under
more scope-specific directories, which helps to avoid circular
dependencies and is just cleaner to navigate and expand in the
future.

Otherwise this is a largely uncritical port to ESM module syntax!
There are probably a number of changes and other cleanups that
remain much needed.

Whenever I make changes to tui-lib it's hard to believe it's
already been <INSERT COUNTING NUMBER HERE> years since the
previous time. First commits are from January 2017, and the
code originates a month earlier in KAaRMNoD!

1 files changed, 1 insertions, 1 deletions

diff --git a/util/count.js b/util/count.js
index 24c11b0..d4c0919 100644
--- a/util/count.js
+++ b/util/count.js
@@ -1,4 +1,4 @@
-module.exports = function count(arr) {
+export default function count(arr) {
   // Counts the number of times the items of an array appear (only on the top
   // level; it doesn't search through nested arrays!). Returns a map of
   // item -> count.