[Enhancement] Docker support Debugging (byebug & pry) and receive emails to MailHog via smtp (#371)

* updated development docker setup

* turned on yarn integrity check

* create test docker compose and update development dockerfile

* create docker Readme.md file

* fix README.md file

* create docker-copmose and dockerfile for production/staging environment setup

* added mailhog to catch email

* remove yarn integrity check in development mode!

* Update Readme.md file to support mailhog inbox

* update link to docker development guide from mail README

* remove .env.development and use .env.example for docker as .env.development was mixing with circleci config

* make the dockerfile configurable like before

* update docker-compose as per suggesion in PR

* create docker setup docs

* Revert accidental deletion

* fix: typo for branding consistency

* fix typo

* update the code as per recommendation in PR

* remove package-lock and add gitignore

* fix vulnerability AND update env for tests to pass

* Fix yarn integrity check across different docker services

* update code based on rubocop and PR suggestions

* remove redundant test docker-compose and dockerfile

* update rails entrypoint, update docs and Gemfile

* [Rubocop] order Gemfile alphabetically

* Reordering Gemfile

.env.example

@@ -1,19 +1,32 @@
+REDIS_URL=redis://redis:6379
+SECRET_KEY_BASE=
+
+# Postgres Database config variables
+POSTGRES_HOST=postgres
+POSTGRES_USERNAME=postgres
+POSTGRES_PASSWORD=
+RAILS_ENV=development
+RAILS_MAX_THREADS=5
+
 #fb app
 FB_VERIFY_TOKEN=
 FB_APP_SECRET=
 FB_APP_ID=
 
 #mail
-MAILER_SENDER_EMAIL=
-SMTP_ADDRESS=
+MAILER_SENDER_EMAIL=accounts@chatwoot.com
+SMTP_PORT=1025
+SMTP_DOMAIN=chatwoot.com
+SMTP_ADDRESS=mailhog
 SMTP_USERNAME=
 SMTP_PASSWORD=
+SMTP_AUTHENTICATION=
+SMTP_ENABLE_STARTTLS_AUTO=
 
 #misc
-FRONTEND_URL=http://localhost:3000
+FRONTEND_URL=http://0.0.0.0:3000
 
 #s3
-
 S3_BUCKET_NAME=
 AWS_ACCESS_KEY_ID=
 AWS_SECRET_ACCESS_KEY=
@@ -23,16 +36,10 @@ AWS_REGION=
 SENTRY_DSN=
 
 ####  This environment variables are only required in hosted version which has billing
-BILLING_ENABLED=
+ENABLE_BILLING=
+
 ## chargebee settings
 CHARGEBEE_API_KEY=
 CHARGEBEE_SITE=
 CHARGEBEE_WEBHOOK_USERNAME=
-CHARGEBEE_WEBHOOK_PASSWORD=
-
-#Database config variables
-POSTGRES_HOST=localhost
-POSTGRES_DATABASE=chatwoot_dev
-POSTGRES_USERNAME=postgres
-POSTGRES_PASSWORD=
-RAILS_MAX_THREADS=5
+CHARGEBEE_WEBHOOK_PASSWORD=