This is actually going to be an issue with your IIS/web.config and not with Kentico.
You need to tell the site what a .svg file is for it's content type. Specifically, you need to set .svg to be the mime type/content type of image/svg+xml
In your Web.config, you'll need to find and add something like the below:
<configuration>
<system.webServer>
<staticContent>
<mimeMap fileExtension=".svg" mimeType="image/svg+xml" />
</staticContent>
</system.webServer>
</configuration>