Vite embedded build of Element Call (#3077)

* Embedded package build of Element Call

Part of https://github.com/element-hq/element-call/issues/2994

This creates a new "embedded" build (vs "full" build) at the vite level. It will be used by a later PR that actually provides platform specific packages.

Embedded build:

- Uses relative URLs
- Uses relative config.json path and other resource loading
- Has a config.json built in
- Doesn't include the public folder (e.g. favicon)

Out of scope:

- this doesn't attempt to exclude SPA functionality, so technically the build could be used in SPA
- the above means that the crypto-wasm binary is included in the build

* CI artifact name based on type of build

* Update src/config/Config.ts

src/config/Config.ts

@@ -29,7 +29,20 @@ export class Config {
       const internalInstance = new Config();
       Config.internalInstance = internalInstance;
 
-      Config.internalInstance.initPromise = downloadConfig("/config.json").then(
+      let fetchTarget: string;
+
+      if (
+        window.location.pathname.endsWith("/room/") ||
+        window.location.pathname.endsWith("/room")
+      ) {
+        // it looks like we are running in standalone mode so use the config at the root
+        fetchTarget = new URL("/config.json", window.location.href).href;
+      } else {
+        // otherwise we are probably running as a widget so use the config in the same directory
+        fetchTarget = "config.json";
+      }
+
+      Config.internalInstance.initPromise = downloadConfig(fetchTarget).then(
         (config) => {
           internalInstance.config = merge({}, DEFAULT_CONFIG, config);
         },
@@ -71,11 +84,8 @@ export class Config {
   private initPromise?: Promise<void>;
 }
 
-async function downloadConfig(
-  configJsonFilename: string,
-): Promise<ConfigOptions> {
-  const url = new URL(configJsonFilename, window.location.href);
-  const response = await fetch(url);
+async function downloadConfig(fetchTarget: string): Promise<ConfigOptions> {
+  const response = await fetch(fetchTarget);
 
   if (isFailure(response)) {
     // Lack of a config isn't an error, we should just use the defaults.