(docs) Examples: Update collaborative-editors README file

The README file has been updated with purpose, prerequisites and running section.

Fixes: 0xTheProDev#67

Signed-off-by: Lakshya Thakur lapstjup@gmail.com

examples/collaborative-editors/README.md

@@ -0,0 +1,34 @@
+## Purpose
+
+This example can help you get familiar with the API usage of `@otjs/firebase-ace` and `@otjs/firebase-monaco`.
+
+## Prerequisites
+
+If you followed the [installation](https://github.com/Progyan1997/Operational-Transformation#installation) steps successfully, you would have `lerna` and `yarn` installed globally.
+
+Before running this example, it's necessary to build all the packages using `yarn build` in the root (Operational-Transformation) directory.
+
+Also, the **_firebase.json_** in this directory has `database` entry where `rules` point to `".firebase/database.rules.json"` file which is not included with this repository. The user can add their own file with custom rules.
+
+For development purpose, the following can be the content of this file :-
+
+```
+{
+    "rules":{
+      ".read":true,
+      ".write":true
+    }
+}
+```
+
+## Running
+
+The example doesn't need the user to be authenticated with **firebase** since it runs local **firebase-emulator** for development purposes.
+
+- Run `yarn start` from the root of this directory to fire up both the emulator and the collaborative-editors UI (accessible at **localhost:8000**).
+  ![Landing Page](../../.github/images/examples/collaborative-editors/LandingPage.png)
+
+- Click on the editor you want to test and you will be redirected to it.
+- Copy the url and paste it in a new tab to open another session.
+- Start collaborating 🤝
+  ![Firebase Monaco editor in action](../../.github/images/examples/collaborative-editors/FirebaseMonaco.png)