Documentation: Add frontmatter to WSL docs

[joewxboy]

The WSL 2 installation instructions page https://open-horizon.github.io/docs/mgmt-hub/docs/WSL/ is currently shown as a top-level navigation item (see screenshot below):

This is because it is missing front matter. Please add the front matter, and ensure the navigation is updated to show the page as falling under advanced manual installation:

---

copyright:
years: 2021 - 2023
lastupdated: "2023-09-26" <-- ensure the right date here
title: "Manual agent install" <-- ensure the right title here

parent: Edge devices info
grand_parent: Edge devices
nav_order: 5
---

[sajdakabir]

Hey @joewxboy, I would like to work on this issue. can you assign it to me?

[joewxboy]

@sajdakabir Sure. Let me know if you have any questions