As best as I can tell, the actual fetching of the sourcemap URLs is done here, and this doesn't allow for any proxy configuration.

Would it be possible to add a check for process.env.http_proxy and process.env.https_proxy here and use those values for the http(s) request?

Currently running this in an environment that requires a proxy spams the debug console with a bunch of lines similar to this:

SourceMaps.loadSourceMapContents: Could not download sourcemap from https://ticino.blob.core.windows.net/sourcemaps/0759f77bb8d86658bc935a10a64f6182c5a1eeba/extensions\extension-editing\out/extensionLinter.js.map