fix(ui): Use a seperate highlight for connectors

* Some colorschemes do some funky things with the comment highlight, most
  notably making them italic, which messes up the outline connector. Fix
  this by copying the foreground color from the comment hl into a new
  highlight.

* Closes #42

lua/symbols-outline/ui.lua

@@ -27,25 +27,40 @@ local function highlight_text(name, text, hl_group)
 end
 
 function M.setup_highlights()
+    -- Setup the FocusedSymbol highlight group if it hasnt been done already by
+    -- a theme or manually set
+    if vim.fn.hlexists('FocusedSymbol') == 0 then
+        vim.cmd 'hi FocusedSymbol term=italic,bold cterm=italic ctermbg=yellow ctermfg=darkblue gui=bold,italic guibg=yellow guifg=darkblue'
+    end
+
+    -- Some colorschemes do some funky things with the comment highlight, most
+    -- notably making them italic, which messes up the outline connector. Fix
+    -- this by copying the foreground color from the comment hl into a new
+    -- highlight.
+    local comment_fg_gui = vim.fn.synIDattr(vim.fn.hlID('SignColumn'), 'fg',
+                                            'gui')
+    local comment_fg_cterm = vim.fn.synIDattr(vim.fn.hlID('SignColumn'), 'fg',
+                                              'cterm')
+
+
+    vim.cmd(string.format('hi SymbolsOutlineConnector ctermfg=%s guifg=%s',
+                          comment_fg_cterm, comment_fg_gui))
+
     local symbols = config.options.symbols
 
     -- markers
-    highlight_text("marker_middle", M.markers.middle, "Comment")
+    highlight_text("marker_middle", M.markers.middle, "SymbolsOutlineConnector")
-    highlight_text("marker_vertical", M.markers.vertical, "Comment")
+    highlight_text("marker_vertical", M.markers.vertical,
-    highlight_text("markers_horizontal", M.markers.horizontal, "Comment")
+                   "SymbolsOutlineConnector")
-    highlight_text("markers_bottom", M.markers.bottom, "Comment")
+    highlight_text("markers_horizontal", M.markers.horizontal,
+                   "SymbolsOutlineConnector")
+    highlight_text("markers_bottom", M.markers.bottom, "SymbolsOutlineConnector")
 
     for _, value in ipairs(symbol_kinds) do
         local symbol = symbols[value]
         highlight_text(value, symbol.icon, symbol.hl)
     end
 
-    -- Setup the FocusedSymbol highlight group if it hasnt been done already by
-    -- a theme or manually set
-    if vim.fn.hlexists('FocusedSymbol') == 0 then
-        vim.cmd(
-            'hi FocusedSymbol term=italic,bold cterm=italic ctermbg=yellow ctermfg=darkblue gui=bold,italic guibg=yellow guifg=darkblue')
-    end
 end
 
 return M