feat: add raw file link in source file browser

templates/repo/source-git.hamlet

@@ -87,7 +87,7 @@ $if not $ null looms
 
 $case sv
   $of SourceFile (FileView name body)
-    <h2>#{name}
+    <h2>#{name} <a href=@{RepoBranchRawR repo ref dir}>[Raw]</a>
     ^{body}
   $of SourceDir (DirectoryView mname ents mreadme)
     <h2>#{fromMaybe "Files" mname}