vscode_extension_dumper: downcase extension names.

VSCode seems to be doing this itself in newer versions so this will
allow for some more consistency.

lib/bundle/vscode_extension_dumper.rb

@@ -10,7 +10,7 @@ def reset!
 
     def extensions
       @extensions ||= if Bundle.vscode_installed?
-        `code --list-extensions 2>/dev/null`.split("\n")
+        `code --list-extensions 2>/dev/null`.split("\n").map(&:downcase)
       else
         []
       end