New user docs.

[Ken D'Ambrosio]

Hey, all.  For $REASONS, I'm getting acquainted with ATS, and I'm 
noticing some bumps in the documentation.  E.g., in 
https://docs.trafficserver.apache.org/en/latest/_sources/getting-started/index.en.rst.txt, 
it's mentioned that ATS is in EPEL... and it's not: 
https://github.com/apache/trafficserver/issues/6855

Also, as another example, "curses" is shown as a requisite package for 
builiding, but it's been replaced by ncurses.

I'd like to cut some PRs for this, but am wondering what the process for 
opening a Jira ticket is (Jira's mentioned here 
(https://cwiki.apache.org/confluence/display/TS/Contributing), but I 
don't see how to actually create a ticket), and submitting a PR.  I have 
no expectation of submitting code fixes, but keeping the docs up-to-date 
can, at least, help new users find their way forward.

Thanks!

-Ken