docs: document mutations API (#228)

---------

Co-authored-by: Michael <small203@morris.umn.edu>

Author: michael-small

apps/demo/src/app/counter-rx-mutation/counter-rx-mutation.ts

@@ -16,6 +16,9 @@ export type CounterResponse = {
   json: { counter: number };
 };
 
+// TODO - rename this file to just be `mutations-functions-standalone` + class/selector etc??
+// And then the other folder to "store"
+// Or maybe put these all in one folder too while we are at it?
 @Component({
   selector: 'demo-counter-rx-mutation',
   imports: [CommonModule],

docs/docs/extensions.md

@@ -12,6 +12,7 @@ It offers extensions like:
 - [Immutable State Protection](./with-immutable-state): Protects the state from being mutated outside or inside the Store.
 - [~Redux~](./with-redux): Possibility to use the Redux Pattern. Deprecated in favor of NgRx's `@ngrx/signals/events` starting in 19.2
 - [Resource](./with-resource): Integrates Angular's Resource into SignalStore for async data operations
+- [Mutations](./mutations): Seek to offer an appropriate equivalent to signal resources for sending data back to the backend
 - [Reset](./with-reset): Adds a `resetState` method to your store
 - [Call State](./with-call-state): Add call state management to your signal stores
 - [Storage Sync](./with-storage-sync): Synchronizes the Store with Web Storage