Added short bot credentials setup guide

Wrote a step-by-step guide for bot credentials in README.md

Also added a comment to explain the auto join being commented out.

README.md

@@ -0,0 +1,14 @@
+# Heimdall
+
+## Description
+*Heimdall* is a matrix bot supposed to control and manage services and containers by simple text commands.
+It is a convenience tool for the own self-hosting empire.
+
+## Setup the bot credentials
+1. Create or get access to a **matrix account** to use as the bot.
+2. Acquire the **access token** and **user id**. You can do this in riot by going into the settings and scrolling down to the very end.
+3. Copy *config.sample.yaml* and name the copy *config.yaml*.
+4. Replace the placeholder values with your own:
+    * Replace the *baseurl* value with the base url of your home server (e.g. *https://example.org*).
+    * Replace the *access token* with your own.
+    * Replace the *user id* with your own.

index.js

@@ -11,6 +11,7 @@ const matrixclient = sdk.createClient({
     userId: config.userid
 });
 
+// Autojoin for the bot (keep commented out when not needed to prevent abuse)
 /*matrixclient.on('RoomMember.membership', function(event, member) {
     if(member.membership === 'invite' && member.userId === userid) {
         matrixclient.joinRoom(member.roomId).done(function() {