improve welcome message with more/better "how to get help" instructions

[brandondees]

I think a very brief summary up top is necessary, but with a series of links to good articles or just a more extended paragraph format explanation of the basics folks should learn, particularly about how to ask for help without being annoying, and how to pick up the basics of slack markdown and so forth, in addition to the welcome message info already available in the resources wiki page

[brandondees]

I have a blog article in the works on the asking for help bits, FWIW