Add example.ps1 (#149) (#150)

shell/example.ps1

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+# Shell integration for Windows Terminal
+#
+# Note:
+# - I couldn't figure out how to override `cd`, so I used `cdir` instead.
+# - To avoid hitting the absolute path length limit, I made the created directories single-digit numbers.
+# - It seems that `&&` can be used in PowerShell 7, but it's not available in version 5, so I omitted the error handling.
+#
+# See:
+# - [about_Profiles - PowerShell | Microsoft Learn](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_profiles?view=powershell-5.1)
+# - [Migrating from Windows PowerShell 5.1 to PowerShell 7 - PowerShell | Microsoft Learn](https://learn.microsoft.com/en-us/powershell/scripting/whats-new/migrating-from-windows-powershell-51-to-powershell-7?view=powershell-7.4#separate-profiles)
+#
+Set-Variable -Option Constant -Name RPG -Value "C:\your\path\to\rpg-cli.exe"
+
+function rpg() {
+    & $RPG $args
+    sync_rpg
+}
+
+function cdir() {
+    & $RPG cd $args
+    sync_rpg
+}
+
+function dn() {
+    $current = (Get-Item $PWD).BaseName
+    if ($current -match "^[0-9]+$") {
+        $next = (([int]$current) + 1) % 10
+        New-Item -ItemType Directory -ErrorAction SilentlyContinue $next > $null
+        cdir $next
+    } elseif (Test-Path "1") {
+        cdir 1
+    } else {
+        New-Item -ItemType Directory -ErrorAction SilentlyContinue "dungeon\1" > $null
+        cdir "dungeon/1"
+    }
+    rpg ls
+}
+
+function sync_rpg() {
+    $pwd = & $RPG pwd
+    Set-Location -Path $pwd
+}