Fix file URIs in toolsService to work with both local and remote workspaces

[curiouscomputer]

Void had an issue where when opening a remote workspace, tools for reading/writing files would refer to local files instead of remote ones.

I modified toolService.ts to check for the remoteAuthority in validateURI, so that if the current workspace is remote, the file path is converted to a remote URI. This fixes the issue described in https://github.com/voideditor/void/issues/640.