docs: add WSL2 setup instructions for Windows users

[sarina-aulakh]

[IMPROVEMENT] Add WSL2 setup instructions for Windows users

In raising this pull request, I confirm the following:

• I have read and understood the contributors guide.
• I have checked that another pull request for this purpose does not exist.
• I have considered, and confirmed that this submission will be valuable to others.
• I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
• I give this submission freely, and claim no ownership to its content.

My familiarity with the project is as follows:

• I have never used the project.

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The current Windows installation section directs users to Cygwin, which
is the legacy method. The 2026 GSoC project goals for Sample Platform NG
specifically mention moving toward WSL2/Docker for Windows users.

This PR adds a WSL2 section above the existing Cygwin instructions,
giving Windows users a modern and recommended setup path.

Changes made:

• Added Windows (Recommended: WSL2) section to install/installation.md
• Includes step-by-step WSL2 setup instructions
• Notes that Cygwin is the legacy method

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[canihavesomecoffee]

Thanks for the PR, but given that the direction of this tool will be to run on a cloud platform only, I don't see any benefits in adding this. Closing the PR.