How can I get my TreeView icons to look good with the VSCode theme?

I'm writing a VSCode extension with a TreeView that has actions associated with it, and those actions have icons:

"contributes": {
        "commands": [
            {
                "command": "computerVision.removeExpression",
                "category": "CV",
                "title": "Remove",
                "icon": "resources/font-awesome/trash-can.svg"
            },
            {
                "command": "computerVision.openView",
                "category": "CV",
                "title": "Open View",
                "icon": "resources/font-awesome/window-restore.svg"
            }
        ]
        ...
}

But this looks like this:

Compare this to the icons in the default source control tab:

How can I get my icons to fit the current theme? I tried setting dark and light versions separately, but that didn't help.