Update guide to mention code linters available
Update guide to mention code linters available

Contributors can run RuboCop locally to catch code style error in Ruby
code and npm lint task for `rails-ujs` CoffeeScript and JavaScript code.

[skip ci]

jeremy/rails,repinel/rails,flanger001/rails,vipulnsward/rails,palkan/rails,flanger001/rails,starknx/rails,joonyou/rails,fabianoleittes/rails,yalab/rails,yahonda/rails,mohitnatoo/rails,repinel/rails,Erol/rails,tjschuck/rails,esparta/rails,joonyou/rails,shioyama/rails,Vasfed/rails,rails/rails,fabianoleittes/rails,joonyou/rails,kmcphillips/rails,illacceptanything/illacceptanything,EmmaB/rails-1,schuetzm/rails,printercu/rails,yahonda/rails,arunagw/rails,vipulnsward/rails,iainbeeston/rails,mechanicles/rails,Erol/rails,Vasfed/rails,tgxworld/rails,betesh/rails,MSP-Greg/rails,yalab/rails,yalab/rails,notapatch/rails,illacceptanything/illacceptanything,illacceptanything/illacceptanything,repinel/rails,kddeisz/rails,georgeclaghorn/rails,notapatch/rails,iainbeeston/rails,schuetzm/rails,arunagw/rails,tgxworld/rails,Edouard-chin/rails,Envek/rails,iainbeeston/rails,yhirano55/rails,illacceptanything/illacceptanything,yawboakye/rails,baerjam/rails,Envek/rails,starknx/rails,rafaelfranca/omg-rails,fabianoleittes/rails,baerjam/rails,Stellenticket/rails,illacceptanything/illacceptanything,shioyama/rails,printercu/rails,eileencodes/rails,illacceptanything/illacceptanything,MSP-Greg/rails,illacceptanything/illacceptanything,printercu/rails,vipulnsward/rails,jeremy/rails,lcreid/rails,Stellenticket/rails,fabianoleittes/rails,Erol/rails,gauravtiwari/rails,Envek/rails,bogdanvlviv/rails,arunagw/rails,yawboakye/rails,kmcphillips/rails,Stellenticket/rails,schuetzm/rails,jeremy/rails,Erol/rails,georgeclaghorn/rails,betesh/rails,illacceptanything/illacceptanything,utilum/rails,illacceptanything/illacceptanything,bogdanvlviv/rails,bogdanvlviv/rails,Edouard-chin/rails,utilum/rails,kmcphillips/rails,lcreid/rails,palkan/rails,tgxworld/rails,vipulnsward/rails,utilum/rails,BlakeWilliams/rails,yhirano55/rails,yhirano55/rails,utilum/rails,tgxworld/rails,Vasfed/rails,prathamesh-sonpatki/rails,prathamesh-sonpatki/rails,starknx/rails,illacceptanything/illacceptanything,eileencodes/rails,illacceptanything/illacceptanything,Envek/rails,illacceptanything/illacceptanything,georgeclaghorn/rails,eileencodes/rails,yalab/rails,BlakeWilliams/rails,gauravtiwari/rails,palkan/rails,palkan/rails,gauravtiwari/rails,mohitnatoo/rails,Vasfed/rails,yahonda/rails,esparta/rails,tjschuck/rails,esparta/rails,prathamesh-sonpatki/rails,kmcphillips/rails,illacceptanything/illacceptanything,tjschuck/rails,esparta/rails,iainbeeston/rails,rafaelfranca/omg-rails,shioyama/rails,rails/rails,yahonda/rails,betesh/rails,eileencodes/rails,illacceptanything/illacceptanything,mohitnatoo/rails,yhirano55/rails,prathamesh-sonpatki/rails,rails/rails,mechanicles/rails,MSP-Greg/rails,shioyama/rails,yawboakye/rails,flanger001/rails,rafaelfranca/omg-rails,flanger001/rails,jeremy/rails,BlakeWilliams/rails,bogdanvlviv/rails,lcreid/rails,Edouard-chin/rails,illacceptanything/illacceptanything,kddeisz/rails,repinel/rails,Edouard-chin/rails,tjschuck/rails,kddeisz/rails,BlakeWilliams/rails,joonyou/rails,schuetzm/rails,notapatch/rails,printercu/rails,baerjam/rails,mechanicles/rails,betesh/rails,yawboakye/rails,Stellenticket/rails,rails/rails,MSP-Greg/rails,mechanicles/rails,EmmaB/rails-1,EmmaB/rails-1,kddeisz/rails,notapatch/rails,baerjam/rails,lcreid/rails,arunagw/rails,mohitnatoo/rails,georgeclaghorn/rails