fix(component): add docs overview (#2444)

* fix(component): add docs overview

closes #2442

* Update projects/ngrx.io/content/guide/component/index.md

Co-Authored-By: Tim Deschryver <28659384+timdeschryver@users.noreply.github.com>

Co-authored-by: Tim Deschryver <28659384+timdeschryver@users.noreply.github.com>

Author: BioPhoton

projects/ngrx.io/content/guide/component/index.md

@@ -1,3 +1,14 @@
 # @ngrx/component
 
-Placeholder
+The Component package is a set of primitive reactive helpers to enable fully reactive, fully zone-less applications.
+
+## Introduction
+
+This package includes primitives that act as the glue in reactive Angular applications.
+They take over rendering and provide reactivity to parts where Angular doesn't out of the box. 
+
+## Key Concepts
+
+Rendering happens in the template only:
+  - [Push Pipe](guide/component/push)
+  - [Let Directive](guide/component/let)

projects/ngrx.io/content/guide/component/let.md

@@ -3,6 +3,8 @@
 The `*ngrxLet` directive serves a convenient way of binding observables to a view context (a dom element scope).
 It also helps with several internal processing under the hood.
 
+Same as [PushPipe](guide/component/push), it also respects ViewEngine as well as Ivy's new rendering API.
+
 The current way of binding an observable to the view looks like that:
 ```html
 <ng-container *ngIf="observableNumber$ as n">

projects/ngrx.io/content/guide/component/push.md

@@ -4,6 +4,8 @@ The `ngrxPush` pipe serves as a drop-in replacement for the `async` pipe.
 It contains intelligent handling of change detection to enable us
 running in zone-full as well as zone-less mode without any changes to the code.
 
+Same as [LetDirective](guide/component/let), it also respects ViewEngine as well as Ivy's new rendering API.
+
 The current way of binding an observable to the view looks like that:
 
 ```html

projects/ngrx.io/content/marketing/docs.md

@@ -62,4 +62,5 @@ It is also often require a steep learning curve, including some good understandi
 - [Router Store](guide/router-store) - Bindings to connect the Angular Router to @ngrx/store.
 - [Entity](guide/entity) - Entity State adapter for managing record collections.
 - [NgRx Data](guide/data) - Extension for simplified entity data management.
+- [NgRx Component](guide/component) - Extension for fully reactive, fully zone-less applications.
 - [Schematics](guide/schematics) - Scaffolding library for Angular applications using NgRx libraries.