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, 0 insertions, 13 deletions

diff --git a/ui/HorizontalBox.js b/ui/HorizontalBox.js
deleted file mode 100644
index f92bf10..0000000
--- a/ui/HorizontalBox.js
+++ /dev/null
@@ -1,13 +0,0 @@
-const DisplayElement = require('./DisplayElement')
-
-module.exports = class HorizontalBox extends DisplayElement {
-  // A box that will automatically lay out its children in a horizontal row.
-
-  fixLayout() {
-    let nextX = 0
-    for (const child of this.children) {
-      child.x = nextX
-      nextX = child.right + 1
-    }
-  }
-}