Problem:
- There is reference to gVim in the usr_02.txt file, even though Nvim
has no built-in GUI.
- `:h help-summary` has a section about optional features (e.g.
`+conceal`) even though such thing does not exist in Nvim (`:h
+conceal` will give E149 error).
Solution:
- Remove reference to gVim.
- Replace the section about optional features with a section about Lua.
d591275db7
