docs: basic readme intro

Author: steverusso

docs/README.md

@@ -2,6 +2,23 @@
 
 [![Go Reference](https://pkg.go.dev/badge/github.com/steverusso/cli.svg)](https://pkg.go.dev/github.com/steverusso/cli)
 
-This is primarily a library to parse command line arguments. Anything it offers in
-addition to that (such as optionally reading values from environment variables as well)
-should be invisible to the user who wants to simply parse command line arguments.
+```shell
+go get github.com/steverusso/cli@latest
+```
+
+## Features
+
+* Lightweight, simple, composable.
+* There are **zero** external dependencies.
+* No required project / file layout or recommended use of a generator.
+* No reflection.
+* Fully POSIX-compliant flags (including short & long versions). (TODO reword and check if true)
+* Inputs can additionally be parsed from environment variables and / or default values.
+* Nested subcommands.
+* Clean, well-formatted help messages by default.
+* Ability to build custom help messages.
+
+> [!NOTE]
+> This is primarily a library to parse command line arguments. Anything it offers in
+> addition to that (such as optionally reading values from environment variables as well)
+> should be invisible to the user who wants to simply parse command line arguments.