add .editorconfig file for contributors that use an ide which supports it
add .editorconfig file for contributors that use an ide which supports it

jj-studio/Backbone-JJRelational,apoutchika/Backbone-JJRelational,sarink/Backbone-JJRelational,fvgoto/Backbone-JJRelational,fvgoto/Backbone-JJRelational,chenghlee/Backbone-JJRelational,apoutchika/Backbone-JJRelational,chenghlee/Backbone-JJRelational,jj-studio/Backbone-JJRelational,sarink/Backbone-JJRelational