[Doc] Update Windows command syntax for PowerShell users in "Run HelloWorld" tutorial

[c-fory]

Issue Description
The current "Run HelloWorld using JavaFX SDK" documentation shows Windows commands using %PATH_TO_FX% syntax. This works for Command Prompt (cmd.exe), but fails in PowerShell (the default shell in Windows 11) where the correct syntax is $env:PATH_TO_FX.
This discrepancy causes confusion for Windows 11 users who follow the tutorial verbatim. When running:
javac --module-path %PATH_TO_FX% --add-modules javafx.controls HelloFX.java
In Powershell, user get error like:
wrong: error: module not found: javafx.controls
Proposed Solution
Add PowerShell-specific syntax examples alongside the existing Command Prompt examples:
javac --module-path "$env:PATH_TO_FX" --add-modules javafx.controls HelloFX.java

[abhinayagarwal]

Would you be interested to create a PR for this?