Runnable env per platform

[vsrs]

This PR adds an option to specify runnables env per platform (win32, linux, etc.):

{
    "rust-analyzer.runnables.extraEnv": [
            {
                "platform": "win32",
                "env": {
                    "SCITER_BIN_FOLDER": "C:\\Projects\\3rd\\sciter-js-sdk\\bin\\windows\\x64",
                }
            },
            {
                "platform":["linux","darwin"],
                "env": {
                    "SCITER_BIN_FOLDER": "/home/vit/Projects/sciter/sciter-js-sdk/bin/linux/x64",
                }
            }
        ]
}

[HKalbasi]

@bors r+

[bors]

📌 Commit 08b3b2a has been approved by HKalbasi

It is now in the queue for this repository.

[bors]

⌛ Testing commit 08b3b2a with merge bc1b0bf...

[bors]

☀️ Test successful - checks-actions
Approved by: HKalbasi
Pushing bc1b0bf to master...