add legacy warning when on page loaded from filesystem

Author: g-harel

public/legacy.ts

@@ -4,10 +4,10 @@ import {XmlElement} from "../editable";
 import {genBlob} from "../internal/gen";
 import {mapPoints} from "../internal/util";
 
-// TODO check if file (ex. file://...)
 const isBrowser = new Function("try {return this===window;}catch(e){ return false;}");
 const isLocalhost = () => location.hostname === "localhost" || location.hostname === "127.0.0.1";
-if (!isBrowser() || (isBrowser() && isLocalhost())) {
+const isFile = () => location.protocol === "file:";
+if (!isBrowser() || isLocalhost() || isFile()) {
     console.warn("You are using the legacy blobs API!\nPlease use 'blobs/v2' instead.");
 }