feat: localization (#196)

* Started adding locale translations :)

* Added some more translations

* Working on translating even more pages

* More translations

* Added test default locale retrieval

* replace `intl.formatMessage` with custom `t` hook

* add more translations

* improve title syntax

* add more translations

* translate admin config page

* translated error messages

* add language selecter

* minor fixes

* improve language handling

* add upcoming languages

* add `crowdin.yml`

* run formatter

---------

Co-authored-by: Steve Tautonico <stautonico@gmail.com>

frontend/src/components/admin/configuration/ConfigurationHeader.tsx

@@ -9,6 +9,7 @@ import {
 } from "@mantine/core";
 import Link from "next/link";
 import { Dispatch, SetStateAction } from "react";
+import { FormattedMessage } from "react-intl";
 import useConfig from "../../../hooks/config.hook";
 import Logo from "../../Logo";
 
@@ -42,7 +43,7 @@ const ConfigurationHeader = ({
           </Link>
           <MediaQuery smallerThan="sm" styles={{ display: "none" }}>
             <Button variant="light" component={Link} href="/admin">
-              Go back
+              <FormattedMessage id="common.button.go-back" />
             </Button>
           </MediaQuery>
         </Group>