Add download-translations.bash script

The script can be used to download the translations from Crowdin.

Change-Id: I295b34ef26d361a493e6fd82501bc70405e04ac1
diff --git a/tools/i18n/.gitignore b/tools/i18n/.gitignore
new file mode 100644
index 0000000..68f35d8
--- /dev/null
+++ b/tools/i18n/.gitignore
@@ -0,0 +1 @@
+crowdin.yml