docs: added note about toSignal (angular#54996)

PR Close angular#54996

adev/src/content/guide/signals/rxjs-interop.md

@@ -28,6 +28,10 @@ Like the `async` pipe, `toSignal` subscribes to the Observable immediately, whic
 
 IMPORTANT: `toSignal` creates a subscription. You should avoid calling it repeatedly for the same Observable, and instead reuse the signal it returns.
 
+### Injection context
+
+`toSignal` by default needs to run in an [injection context](guide/di/dependency-injection-context), such as during construction of a component or service. If an injection context is not available, you can manually specify the `Injector` to use instead.
+
 ### Initial values
 
 Observables may not produce a value synchronously on subscription, but signals always require a current value. There are several ways to deal with this "initial" value of `toSignal` signals.

aio/content/guide/rxjs-interop.md

@@ -33,6 +33,10 @@ export class Ticker {
 Like the `async` pipe, `toSignal` subscribes to the Observable immediately, which may trigger side effects. The subscription created by
 `toSignal` automatically unsubscribes from the given Observable upon destruction of the component in which `toSignal` is called.
 
+### Injection context
+
+`toSignal` by default needs to run in an [injection context](/guide/dependency-injection-context), such as during construction of a component or service. If an injection context is not available, an `Injector` can instead be explicitly specified.
+
 ### Initial values
 
 Observables may not produce a value synchronously on subscription, but signals always require a current value. There are several ways to deal with this "initial" value of `toSignal` signals.