Add Windows PowerShell fallback support when pwsh is unavailable

[Copilot]

The extension previously hardcoded the use of pwsh (PowerShell 7+) as the PowerShell executable, which would fail in environments where only Windows PowerShell 5.1 (powershell.exe) is available. This is common in enterprise Windows environments where PowerShell 7+ hasn't been deployed yet.

Changes Made

• Replaced hardcoded executable: Removed the static POWERSHELL_EXECUTABLE = 'pwsh' constant
• Added dynamic detection: Implemented detectPowerShellExecutable() method that:
  1. First attempts to use pwsh (PowerShell 7+)
  2. Falls back to powershell (Windows PowerShell 5.1) if pwsh is unavailable
  3. Caches the detected executable to avoid repeated detection calls
• Enhanced error handling: Added testExecutable() method with improved error messages
• Updated all execution paths: Modified executeScript() and isPowerShellAvailable() methods to use the fallback logic

Example Behavior

Before (fails on Windows without PowerShell 7+):

Error: spawn pwsh ENOENT

After (automatically falls back):

Using PowerShell executable: powershell
Detected PowerShell version using powershell: 5.1.19041.4648

Testing

• ✅ Verified compatibility with PowerShell 7+ environments (existing functionality preserved)
• ✅ Validated fallback logic for Windows PowerShell scenarios
• ✅ Confirmed localization parsing continues to work correctly
• ✅ Extension builds and packages successfully

The extension now works seamlessly across different Windows PowerShell configurations without requiring users to install PowerShell 7+.

Fixes #6.

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[HeyItsGilbert]

@copilot please update the changelog also

[Copilot]

@copilot please update the changelog also

Updated CHANGELOG.md with the PowerShell fallback support feature. Added entry under "Unreleased" section documenting the new automatic detection and fallback functionality that enables compatibility with Windows PowerShell 5.1 environments. (commit 38e495c)