Add Windows PowerShell port of statusline script

[aconite33]

Adds a PowerShell port of statusline.sh for Windows users, along with updated README documentation covering installation on both
platforms.

• scripts/statusline.ps1 - full port of the bash statusline, compatible with PowerShell 5.1+
• README.md - statusline section updated with Windows install steps and platform-specific settings.json examples

Changes

scripts/statusline.ps1

• Functionally equivalent to statusline.sh - same two-line layout, same data, same color coding
• Uses ConvertFrom-Json for JSON parsing (no jq requirement)
• Git is optional - gracefully skips branch/repo info if git is not installed
• Uses ASCII-safe progress bar characters (# and -) for broad terminal compatibility
• Forces UTF-8 output encoding for consistent rendering

README.md

• Statusline section now shows install instructions for both macOS/Linux and Windows
• Adds settings.json examples for both platforms

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}