i18n: Use gettext function instead of wrapper

No need to deviate from the default here.

Part-of: <https://gitlab.gnome.org/Incubator/loupe/-/merge_requests/170>

src/util/gettext.rs

@@ -0,0 +1,14 @@
+pub use gettextrs::gettext;
+
+fn freplace(mut s: String, args: &[&str]) -> String {
+    for arg in args {
+        s = s.replacen("{}", arg, 1);
+    }
+
+    s
+}
+
+pub fn gettext_f(format: &str, args: &[&str]) -> String {
+    let s = gettextrs::gettext(format);
+    freplace(s, args)
+}