Create documentation for changing `$HOME` path on Windows

Windows users that have a `$HOME` path that points to a network drive location will experience difficulties using Git and Git Bash. Some of these difficulties include:

- Very slow Git commands

This can happen when Git/Git Bash is installed on the network drive or when running commands from a network drive location.

- Permissions errors

Sometimes these network drives are read-only, so commands like `git config` will return a `PERMISSION DENIED` error.

The following should fix these problems:

1. Open a Command Prompt window (Open the Start menu, type `cmd`, and press return)
1. Run the following command:

```
setx HOME "%USERPROFILE%"
```

1. Press return. You should see `SUCCESS: Specified value was saved.`
1. Close the Command Prompt window
1. Open Git Bash or restart it if it was already open