Add bundle install step to the getting started guide

content/v2.0/introduction/getting-started.md

@@ -120,6 +120,7 @@ We'll see this structure in more detail as this guide progresses.
 For now let's get our new application running. In the bookshelf directory, run:
 
 ```shell
+$ bundle install
 $ hanami server
 ```
 

content/v2.1/introduction/getting-started.md

@@ -141,6 +141,7 @@ We'll see this structure in more detail as this guide progresses.
 For now let's get our new app running. In the bookshelf directory, run:
 
 ```shell
+$ bundle install
 $ bundle exec hanami dev
 ```
 

content/v2.2/introduction/getting-started.md

@@ -143,6 +143,7 @@ We'll see this structure in more detail as this guide progresses.
 For now let's get our new app running. In the bookshelf directory, run:
 
 ```shell
+$ bundle install
 $ bundle exec hanami dev
 ```