OJT21-52: Add pre-commit and rubocop auto-fix

+repos:
+- repo: local
+  hooks:
+    - id: rubocop
+      name: Check Ruby style with rubocop
+      description: Enforce Ruby style guide with rubocop and rubocop-rspec
+      entry: rubocop
+      language: ruby
+      types: ['ruby']
+      args: ['--safe', '--auto-correct-all','--disable-uncorrectable', '--force-exclusion']
\ No newline at end of file

 # README
 
--DEVELOPMENT:
-    -Create a mysql_account.rb file in config folder and put your mysql credentials with the following format:
-    .article {
-            # frozen_string_literal: true
+## DEVELOPMENT ##
+        - Create a mysql_account.rb file in config folder and put your mysql credentials with the following format:
+                > # frozen_string_literal: true
 
-            ENV['MYSQL_USERNAME'] = 'your_user_name'
-            ENV['MYSQL_PASSWORD'] = 'your_password'
-    }
+                > ENV['MYSQL_USERNAME'] = 'your_user_name'
+                > ENV['MYSQL_PASSWORD'] = 'your_password'
+
+        - Install pre-commit application. You can follow here https://pre-commit.com/#install. We already provided the config.yaml.
+                - Input this command in the terminal in the root of the api:
+                        _pre-commit install --instal-hooks_
+