windows: Fix eslint installation (#15331)

Close #13786. To make `eslint` running on Windows, I made the following
changes:

1. Ensure that `zed` downloads the `.zip` file.
2. Handle the `$shared` symbolic link by copying files to the link
location.
3. In #13891, I mentioned that the `npm` `post-install` script was
always failing. After debugging, I found it was due to missing
environment variables. This has been fixed, and I will submit a new PR
to address the changes in #13891.

With this PR, `eslint` can now successfully run on Windows. Video:



https://github.com/user-attachments/assets/e85451b8-0388-490a-8a75-01c12d744f7c



Release Notes:

- Fixed `eslint` not running on Windows
([#13786](https://github.com/zed-industries/zed/issues/13786)).

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/node_runtime/src/node_runtime.rs

@@ -290,6 +290,13 @@ impl NodeRuntime for RealNodeRuntime {
                 {
                     command.env("SYSTEMROOT", val);
                 }
+                // Without ComSpec, the post-install will always fail.
+                if let Some(val) = std::env::var("ComSpec")
+                    .context("Missing environment variable: ComSpec!")
+                    .log_err()
+                {
+                    command.env("ComSpec", val);
+                }
                 command.creation_flags(windows::Win32::System::Threading::CREATE_NO_WINDOW.0);
             }