[#11003] First attempt to use the first-interaction action to provide welcome messages to new contributors.
[#11003] First attempt to use the first-interaction action to provide
welcome messages to new contributors.

The messages are slightly different for PRs versus issues.

astropy/astropy,pllim/astropy,pllim/astropy,StuartLittlefair/astropy,lpsinger/astropy,larrybradley/astropy,StuartLittlefair/astropy,dhomeier/astropy,StuartLittlefair/astropy,dhomeier/astropy,pllim/astropy,lpsinger/astropy,larrybradley/astropy,mhvk/astropy,larrybradley/astropy,mhvk/astropy,pllim/astropy,StuartLittlefair/astropy,astropy/astropy,lpsinger/astropy,StuartLittlefair/astropy,mhvk/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,larrybradley/astropy,aleksandr-bakanov/astropy,mhvk/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,dhomeier/astropy,astropy/astropy,dhomeier/astropy,lpsinger/astropy,aleksandr-bakanov/astropy,saimn/astropy,saimn/astropy,saimn/astropy,astropy/astropy,saimn/astropy,pllim/astropy,saimn/astropy,mhvk/astropy,dhomeier/astropy,astropy/astropy