Add new macro importing translation to the final binary

Add a new macro include_i18n!, taking similar arguments to i18n(),
and expanding to the same type. It allow to include translations in
the final binary, so that once compiled, it can be run from anywhere,
without depending on `.mo`s to be present

src/lib.rs

@@ -124,6 +124,27 @@ pub fn i18n(domain: &str, lang: Vec<&'static str>) -> Translations {
     })
 }
 
+#[macro_export]
+macro_rules! include_i18n {
+    ( $domain:tt, [$($lang:tt),*] ) => {
+        {
+            use $crate::Catalog;
+            vec![
+            $(
+                (
+                    $lang,
+                    Catalog::parse(
+                        &include_bytes!(
+                            concat!(env!("CARGO_MANIFEST_DIR"), "/translations/", $lang, "/LC_MESSAGES/", $domain, ".mo")
+                            )[..]
+                        ).expect("Error while loading catalog")
+                )
+            ),*
+            ]
+        }
+    }
+}
+
 #[cfg(feature = "build")]
 pub fn update_po(domain: &str, locales: &[&'static str]) {
     use std::{path::Path, process::Command};