crowdin: Update readme

* lxml is also needed

Change-Id: Ia486a90b8f1cf7bdc5251f2e4237582445b8ce6f
diff --git a/README.mkdn b/README.mkdn
index 04f65c1..ad72674 100644
--- a/README.mkdn
+++ b/README.mkdn
@@ -14,9 +14,9 @@
     echo 'deb https://artifacts.crowdin.com/repo/deb/ /' | sudo tee /etc/apt/sources.list.d/crowdin.list > /dev/null
     sudo apt-get update && sudo apt-get install crowdin
 
-python-git is used for Git integration, python-yaml is used for parsing configuration files:
+The following tools are also required to run the tool:
 
-    sudo apt-get install python-git python-yaml
+    sudo apt-get install python-git python-yaml python-lxml
 
 Copy <lineage_version>_extra_packages.xml to .repo/local_manifests of each <lineage_version> tree
 to make sure you sync all the extra packages not included in the main manifest.