docs(README): add motivation section

Author: boneskull

README.md

@@ -482,6 +482,10 @@ const plain = stripAnsi('\x1b[32m--verbose\x1b[0m'); // '--verbose'
 const customTheme = { ...themes.ocean, colors: { flag: ansi.green } };
 ```
 
+## Motivation
+
+I've always reached for [yargs](https://github.com/yargs/yargs) in my CLI projects. However, I find myself repeatedly doing the same things; I have a sort of boilerplate in my head, ready to go (`requiresArg: true` and `nargs: 1`, amirite?). I don't want boilerplate in my head. I wanted to distill my chosen subset of yargs' behavior into a composable API. And so **bargs** was begat.
+
 ## License
 
 Copyright © 2025 [Christopher "boneskull" Hiller](https://github.com/boneskull). Licensed under the [Blue Oak Model License 1.0.0](./LICENSE).

cspell.json

@@ -53,7 +53,9 @@
     "Sorhus",
     "linkification",
     "linkifying",
-    "wallabyjs"
+    "wallabyjs",
+    "ptmux",
+    "nargs"
   ],
   "words": [
     "bupkis",
@@ -62,7 +64,6 @@
     "linkifies",
     "linkify",
     "positionals",
-    "ptmux",
     "subcommand",
     "subcommands"
   ]