[#23] User guide (PR #24)
[#23] User guide (PR #24)

* updated from level 1

* improved formatting with less blockquotes

se-edu/addressbook-level2,cheec/addressbook-level2,zachylimwl/addressbook-level2,mingruimingrui/addressbook-level2,cheec/addressbook-level2,zachylimwl/addressbook-level2,se-edu/addressbook-level2,mingruimingrui/addressbook-level2,imhongw/addressbook-level2,imhongw/addressbook-level2