feat(colors): highlight gitconfig like toml

Git config and TOML have somewhat similar structure. Because of this,
I'm making gitconfig follow that style.

colors/highlite.vim

@@ -667,7 +667,10 @@ local highlight_groups = {
 	gitcommitOverFlow = 'Error',
 	gitcommitSummary  = 'Title',
 	gitconfigAssignment = 'String',
-	gitconfigNone  = 'Oprator',
+	gitconfigEscape = 'SpecialChar',
+	gitconfigNone  = 'Operator',
+	gitconfigSection = 'Structure',
+	gitconfigVariable = 'Label',
 	gitrebaseBreak = 'Keyword',
 	gitrebaseCommit = 'Tag',
 	gitrebaseDrop = 'Exception',