docs: added docs on readme help indexing

lua/lazy/core/config.lua

@@ -75,9 +75,13 @@ M.defaults = {
       },
     },
   },
+  -- lazy can generate helptags from the headings in markdown readme files,
+  -- so :help works even for plugins that don't have vim docs.
+  -- when the readme opens with :help it will be correctly displayed as markdown
   readme = {
     root = vim.fn.stdpath("state") .. "/lazy/readme",
     files = { "README.md" },
+    -- only generate markdown helptags for plugins that dont have docs
     skip_if_doc_exists = true,
   },
   debug = false,