🚨(i18n) add linter to i18n package

We need to add a linter to the i18n package, we are mainly
interested by the jest linting rules so we create
a jest eslint config pluggable our other configs and to the
i18n eslint config.

src/frontend/.prettierrc.js

@@ -0,0 +1,7 @@
+module.exports = {
+  semi: true,
+  trailingComma: 'all',
+  singleQuote: true,
+  printWidth: 80,
+  tabWidth: 2,
+};