Add initial 11ty website structure

website/node_modules/is-decimal/index.js

@@ -0,0 +1,13 @@
+/**
+ * Check if the given character code, or the character code at the first
+ * character, is decimal.
+ *
+ * @param {string|number} character
+ * @returns {boolean} Whether `character` is a decimal
+ */
+export function isDecimal(character) {
+  const code =
+    typeof character === 'string' ? character.charCodeAt(0) : character
+
+  return code >= 48 && code <= 57 /* 0-9 */
+}