doc: add hitest notes and add termguicolors to example setups

README.md

@@ -62,6 +62,9 @@ Setup should be run in a lua file or in a lua heredoc [:help lua-heredoc](https:
 vim.g.loaded_netrw = 1
 vim.g.loaded_netrwPlugin = 1
 
+-- set termguicolors to enable highlight groups
+vim.opt.termguicolors = true
+
 -- empty setup using defaults
 require("nvim-tree").setup()
 

doc/nvim-tree-lua.txt

@@ -69,6 +69,9 @@ Setup should be run in a lua file or in a |lua-heredoc| if using in a vim file.
     vim.g.loaded_netrw = 1
     vim.g.loaded_netrwPlugin = 1
 
+    -- set termguicolors to enable highlight groups
+    vim.opt.termguicolors = true
+
     -- empty setup using defaults
     require("nvim-tree").setup()
 
@@ -1337,6 +1340,9 @@ Example (in your `init.vim`):
 You should have 'termguicolors' enabled, otherwise, colors will not be
 applied.
 
+To view the active highlight groups run `:so $VIMRUNTIME/syntax/hitest.vim`
+as per |:highlight|
+
 Default linked group follows name.
 
 NvimTreeSymlink