Add i18n, use default imports for UI.

src/context/Locale.tsx

@@ -0,0 +1,14 @@
+import { IntlProvider } from "preact-i18n";
+import definition from "../../external/lang/en.json";
+
+interface Props {
+    children: JSX.Element | JSX.Element[]
+}
+
+export default function Locale({ children }: Props) {
+    return (
+        <IntlProvider definition={definition}>
+            { children }
+        </IntlProvider>
+    )
+}