Add Docs Shell to TW onboarding template
This MR updates the TW onboarding template to add a step for installing the Docs Shell, to help new TWs obtain and install the needed tools for working on the GitLab product documentation.
(The MR also changes some ordered items to unordered items, and it's enough to just say "do these things" without stating a specific order in which they should be done.)
Closes #233 (closed)
Edited by Marcia Ramos