fix: resolve windows command syntax error in lit:copy-spec

[Dijo-404]

Changes

This is a fix for issue: cant run frontend error in renderers\lit:copy-spec] #315

• Added shx as a devDependency: Added this cross-platform wrapper to provide Unix shell command compatibility on Windows, ensuring build scripts run across all operating systems.
• Updated the copy-spec command:
  • From: "mkdir -p src/0.8/schemas && cp ../../specification/0.8/json/*.json src/0.8/schemas"
  • To: "shx mkdir -p src/0.8/schemas && shx cp ../../specification/0.8/json/*.json src/0.8/schemas"

Verification

• Verified that the script executes successfully on Windows environments using cmd.exe.
• Confirmed that functionality remains unchanged on Unix-based systems (Linux/Arch).

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[SimonLai-28198]

Thank you, it helps!