chore: update livebook example to use last version of resvg and new font path

- bump resvg version in readme

Author: mrdotb

README.md

@@ -19,7 +19,7 @@ by adding `resvg_nif` to your list of dependencies in `mix.exs`:
 ```elixir
 def deps do
   [
-    {:resvg, "~> 0.3.0"}
+    {:resvg, "~> 0.4.0"}
   ]
 end
 ```

livebooks/example.livemd

@@ -2,8 +2,8 @@
 
 ```elixir
 Mix.install([
-  {:resvg, "~> 0.3"},
-  {:req, "~> 0.3"},
+  {:resvg, "~> 0.4"},
+  {:req, "~> 0.5"},
   {:kino, "~> 0.9"}
 ])
 ```
@@ -60,7 +60,7 @@ roboto_path = "#{path}/roboto.ttf"
 
 font_file =
   H.download_as!(
-    "https://raw.githubusercontent.com/mrdotb/resvg_nif/master/test/support/fonts/Roboto/Roboto-Regular.ttf",
+    "https://raw.githubusercontent.com/mrdotb/resvg_nif/master/test/support/fonts/Roboto-Regular.ttf",
     roboto_path
   )