Add Pontoon configuration file

Pontoon is the translation platform we will use in the future to translate the
extension strings. This change adds the configuration file.

Bug: twpowertools:40
Change-Id: I7775a7abf28db1f41c4ceba7bb70dc2c6711fa60
diff --git a/i18n-config.toml b/i18n-config.toml
new file mode 100644
index 0000000..4cf7914
--- /dev/null
+++ b/i18n-config.toml
@@ -0,0 +1,17 @@
+base_path = "."
+
+locales = [
+  "ca",
+  "es",
+  "ru",
+  "pt_BR",
+  "pt_PT",
+]
+
+branches = [
+  "master",
+]
+
+[[paths]]
+  reference = "src/static/_locales/en/messages.json"
+  l10n = "src/static/_locales/{locale}/messages.json"