Update VALIDATION-COMMANDS.md with PowerShell equivalents for Windows support (#531)

Author: tmeschter

claude/skills/azure-deployment-preflight/references/VALIDATION-COMMANDS.md

@@ -241,6 +241,7 @@ bicep build <bicep-file> [options]
 
 **Examples:**
 
+**Bash:**
 ```bash
 # Validate syntax (output to stdout, no file created)
 bicep build main.bicep --stdout > /dev/null
@@ -252,6 +253,18 @@ bicep build main.bicep --outdir ./build
 for f in *.bicep; do bicep build "$f" --stdout; done
 ```
 
+**PowerShell:**
+```powershell
+# Validate syntax (output to stdout, no file created)
+bicep build main.bicep --stdout | Out-Null
+
+# Build to specific directory
+bicep build main.bicep --outdir ./build
+
+# Validate multiple files
+Get-ChildItem -Filter *.bicep | ForEach-Object { bicep build $_.FullName --stdout }
+```
+
 **Error Output Format:**
 ```
 /path/to/file.bicep(22,51) : Error BCP064: Found unexpected tokens in interpolated expression.
@@ -372,8 +385,17 @@ targetScope = 'tenant'
 | Bicep CLI | 0.4.0 | Latest | Best error messages |
 
 **Check versions:**
+
+**Bash:**
 ```bash
 az --version
 azd version
 bicep --version
 ```
+
+**PowerShell:**
+```powershell
+az --version
+azd version
+bicep --version
+```