Support any String.Chars.t on extras

Author: josevalim

lib/ex_doc/formatter/html.ex

@@ -627,7 +627,7 @@ defmodule ExDoc.Formatter.HTML do
         {base, text_to_id(Path.rootname(base))}
 
       {path, opts} ->
-        base = path |> Atom.to_string() |> Path.basename()
+        base = path |> to_string() |> Path.basename()
         {base, opts[:filename] || text_to_id(Path.rootname(base))}
     end)
   end

test/ex_doc/formatter/html_test.exs

@@ -519,7 +519,7 @@ defmodule ExDoc.Formatter.HTMLTest do
         doc_config(context,
           extras: [
             "test/fixtures/PlainTextFiles.md",
-            "test/fixtures/LICENSE": [filename: "linked-license"],
+            {"test/fixtures/LICENSE", filename: "linked-license"},
             "test/fixtures/PlainText.txt": [filename: "plain_text"]
           ]
         )