feature (3d): embed 3d viewer anywhere

This contains a bunch of things packaged in 1:

1) UI improvements for the 3D viewer to support all sort of file types
   and create a nice rendering in a clean way with all sort of options

2) enable people to use Filestash as an SDK so we can embed the 3d viewer
   elsewhere

public/assets/helpers/sdk.js

@@ -0,0 +1,15 @@
+// feature detection if we're using Filestash as a standalone app or as an SDK
+// see: ../index.js
+
+export function isSDK() {
+    const importURL = new URL(import.meta.url);
+    return location.origin !== importURL.origin;
+}
+
+export function urlSDK(url) {
+    const importURL = new URL(import.meta.url);
+    if (new RegExp("^/").test(url) === false) {
+        url = "/" + url
+    }
+    return importURL.origin + url;
+}