Update install-copilot-extension.md for neovim on Windows

[kimfaint]

replace line continuation character and home directory variable

Why:

Closes:

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[Copilot]

Pull Request Overview

This PR updates the Neovim and Vim installation instructions for Windows by replacing Unix-style line continuation and home directory syntax with Windows-appropriate equivalents.

• Replaces backslash (\) line continuation with caret (^) for Windows command line
• Replaces $HOME environment variable with %USERPROFILE% for Windows paths

[github-actions]

How to review these changes 👓

Thank you for your contribution. To review these changes, choose one of the following options:

• Spin up a codespace
• Set up a local development environment

A Hubber will need to deploy your changes internally to review.

Table of review links

Note: Please update the URL for your staging server or codespace.

The table shows the files in the content directory that were changed in this pull request. This helps you review your changes on a staging server. Changes to the data directory are not included in this table.

Source	Review	Production	What Changed
copilot/how-tos/set-up/install-copilot-extension.md	fpt ghec	fpt ghec

Key: fpt: Free, Pro, Team; ghec: GitHub Enterprise Cloud; ghes: GitHub Enterprise Server

🤖 This comment is automatically generated.

[Sharra-writes]

@kimfaint Sorry, I forgot to leave a comment to say I was looking into this. But I looked into it, and yes, your change would be at least marginally better, so we're going to go with it. 👍 I'll get this added to the merge queue once checks are passing.

[github-actions]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues ⚡