Note about calling Sentry.init() only once

Author: maxkosty

docs/platforms/javascript/common/configuration/micro-frontend-support.mdx

@@ -14,6 +14,8 @@ keywords:
 If your frontend includes JavaScript bundles from multiple sources with
 different release cycles, you may want to identify these or route events to specific projects. This is especially useful if you've set up [module federation](https://module-federation.github.io/) or a similar frontend architecture.
 
+Below we offer two approaches. Please note that `Sentry.init()` must be called only once, doing otherwise will result in undefined behavior.
+
 ## Automatically Route Errors to Different Projects Depending on Module
 
 `ModuleMetadata` and `makeMultiplexedTransport` can be used together to automatically route