Year-end reminder: switch to Chapel Discourse

[Brad C. <bra...@hp...>]

Hello Chapel Community —

This is a final reminder for 2020 that we're in the process of retiring 
these SourceForge-based Chapel mailing lists in favor of our new Discourse 
site:

 	https://chapel.discourse.group/

If you are interested in keeping in touch with the Chapel community, 
please be sure to register there, as these mailing lists will be going 
away very soon.

Since my last message:

* We've made the Discourse site publicly readable such that you don't need
   to register to browse its contents (though you still do to post)

* We've posted some instructions on how to use Discourse like a mailing
   list, which can be used to recreate the experience of these mailing
   lists for those who aren't attracted to web-based forums:

 	https://chapel.discourse.group/t/welcome-to-the-chapel-programming-language-discourse-page/8

* We've added the ability to sign into the site using your GitHub
   credentials to avoid having to create a new account from scratch.


Best wishes for the end of 2020 and the start of the new year,
-Brad