Update project source_url; fix source_url_pattern

mix.exs

@@ -2,7 +2,8 @@ defmodule Pandoc.MixProject do
   use Mix.Project
 
   @version "0.3.2"
-  @source_url "https://webdevcat.me/git/pandoc/"
+  @source_ref "trunk"
+  @source_url "https://git.miti.sh/ccm/pandoc"
 
   def project do
     [
@@ -18,9 +19,10 @@ defmodule Pandoc.MixProject do
         licenses: ["MIT"]
       ],
       source_url: @source_url,
-      source_url_pattern: "#{@source_url}tree/%{path}#n%{line}",
       docs: [
-        main: "Pandoc"
+        main: "Pandoc",
+        source_ref: @source_ref,
+        source_url_pattern: "#{@source_url}/src/branch/#{@source_ref}/%{path}#L%{line}"
       ],
       aliases: [test: ["pandoc.install --if-missing", "test"]]
     ]