update stan_highlight_rules.js
update stan_highlight_rules.js

- incorporated update from https://github.com/jrnold/rstudio/blob/feature/stan/src/gwt/acesupport/acemode/stan_highlight_rules.js
- updated language to Stan modeling language version 2.6

john-r-mcpherson/rstudio,githubfun/rstudio,suribes/rstudio,edrogers/rstudio,john-r-mcpherson/rstudio,brsimioni/rstudio,jzhu8803/rstudio,brsimioni/rstudio,maligulzar/Rstudio-instrumented,githubfun/rstudio,JanMarvin/rstudio,more1/rstudio,john-r-mcpherson/rstudio,JanMarvin/rstudio,pssguy/rstudio,jar1karp/rstudio,john-r-mcpherson/rstudio,piersharding/rstudio,thklaus/rstudio,githubfun/rstudio,vbelakov/rstudio,tbarrongh/rstudio,pssguy/rstudio,jzhu8803/rstudio,suribes/rstudio,vbelakov/rstudio,piersharding/rstudio,jar1karp/rstudio,sfloresm/rstudio,piersharding/rstudio,suribes/rstudio,jrnold/rstudio,maligulzar/Rstudio-instrumented,githubfun/rstudio,jrnold/rstudio,piersharding/rstudio,edrogers/rstudio,JanMarvin/rstudio,jar1karp/rstudio,pssguy/rstudio,jar1karp/rstudio,vbelakov/rstudio,githubfun/rstudio,sfloresm/rstudio,pssguy/rstudio,tbarrongh/rstudio,tbarrongh/rstudio,sfloresm/rstudio,john-r-mcpherson/rstudio,jar1karp/rstudio,suribes/rstudio,suribes/rstudio,JanMarvin/rstudio,more1/rstudio,tbarrongh/rstudio,JanMarvin/rstudio,thklaus/rstudio,john-r-mcpherson/rstudio,more1/rstudio,pssguy/rstudio,brsimioni/rstudio,suribes/rstudio,maligulzar/Rstudio-instrumented,sfloresm/rstudio,piersharding/rstudio,jrnold/rstudio,jrnold/rstudio,piersharding/rstudio,jzhu8803/rstudio,sfloresm/rstudio,jzhu8803/rstudio,suribes/rstudio,brsimioni/rstudio,john-r-mcpherson/rstudio,more1/rstudio,edrogers/rstudio,tbarrongh/rstudio,jrnold/rstudio,brsimioni/rstudio,JanMarvin/rstudio,jrnold/rstudio,jar1karp/rstudio,thklaus/rstudio,thklaus/rstudio,vbelakov/rstudio,john-r-mcpherson/rstudio,thklaus/rstudio,piersharding/rstudio,pssguy/rstudio,jar1karp/rstudio,jrnold/rstudio,edrogers/rstudio,piersharding/rstudio,vbelakov/rstudio,pssguy/rstudio,sfloresm/rstudio,jzhu8803/rstudio,jrnold/rstudio,maligulzar/Rstudio-instrumented,jrnold/rstudio,vbelakov/rstudio,sfloresm/rstudio,tbarrongh/rstudio,jzhu8803/rstudio,maligulzar/Rstudio-instrumented,githubfun/rstudio,more1/rstudio,maligulzar/Rstudio-instrumented,piersharding/rstudio,edrogers/rstudio,edrogers/rstudio,thklaus/rstudio,thklaus/rstudio,suribes/rstudio,githubfun/rstudio,jar1karp/rstudio,jar1karp/rstudio,tbarrongh/rstudio,JanMarvin/rstudio,pssguy/rstudio,brsimioni/rstudio,thklaus/rstudio,brsimioni/rstudio,sfloresm/rstudio,edrogers/rstudio,tbarrongh/rstudio,JanMarvin/rstudio,JanMarvin/rstudio,maligulzar/Rstudio-instrumented,maligulzar/Rstudio-instrumented,edrogers/rstudio,jzhu8803/rstudio,more1/rstudio,vbelakov/rstudio,more1/rstudio,githubfun/rstudio,vbelakov/rstudio,jzhu8803/rstudio,brsimioni/rstudio,more1/rstudio,maligulzar/Rstudio-instrumented