chore(cli): add USAGE and NOTES section in --help

Author: numToStr

emmylua.md

@@ -436,6 +436,7 @@ You can also define a (pseudo) enum using [`---@alias`](#alias).
 local U = {}
 
 ---@alias VMode
+---Vim operator-mode motions. Read `:h map-operator`
 ---| 'line' Vertical motion
 ---| 'char' Horizontal motion
 ---| 'v'
@@ -452,6 +453,7 @@ return U
 
 ```help
 VMode                                                                    *VMode*
+    Vim operator-mode motions. Read `:h map-operator`
 
     Variants: ~
         ('line')  Vertical motion

src/cli.rs

@@ -97,6 +97,14 @@ OPTIONS:
     -c, --prefix-class      Prefix ---@class tag with return/mod name
     -h, --help              Print help information
     -v, --version           Print version information
+
+USAGE:
+    {NAME} /path/to/first.lua /path/to/second.lua > doc.txt
+    {NAME} -c -a /path/to/{{first,second,third}}.lua > doc.txt
+
+NOTES:
+    - The order of parsing + rendering relative to the given files
+    - Types and Functions will be prefixed with ---@mod name
 "
         );
     }