feat(translations): add i18n support via i18next

* Add i18next integration and i18n config to package.json.
* Add GitHub Actions workflows for Transifex i18n push/pull.
* Mark UI strings as translatable in SearchBar,
  AutocompleteSearchBar, EmptyResults, Error,
  RangeFacet, ResultsPerPage, Sort, SortBy, SortOrder.
* Extract translation template (translations.pot).
* Generate PO files and compiled JSON for 30 locales.
* re-lock

Co-authored-by: Sarah Wiechers <sarah.wiechers@uni-muenster.de>

Author: Samk13

.github/workflows/i18n-pull.yml

@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2023 Graz University of Technology.
+#
+# React-Searchkit is free software; you can redistribute it and/or modify it
+# under the terms of the MIT License; see LICENSE file for more details.
+
+name: i18n:pull translations
+on: workflow_dispatch # manually trigger
+
+jobs:
+  i18n-pull:
+    uses: inveniosoftware/invenio-i18n/.github/workflows/i18n-pull-base.yml@master
+    secrets: inherit

.github/workflows/i18n-push.yml

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+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2023 Graz University of Technology.
+#
+# React-Searchkit is free software; you can redistribute it and/or modify it
+# under the terms of the MIT License; see LICENSE file for more details.
+
+name: i18n:push translations
+on: workflow_dispatch # manually trigger
+
+jobs:
+  i18n-extract:
+    uses: inveniosoftware/invenio-i18n/.github/workflows/i18n-push-base.yml@master
+    with:
+      extract-backend: false
+      frontend-package-path: "./"
+    secrets: inherit

.tx/config

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+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2019 CERN.
+# Copyright (C) 2019 Northwestern University.
+# Copyright (C) 2023 Graz University of Technology.
+#
+# React-Searchkit is free software; you can redistribute it and/or modify it
+# under the terms of the MIT License; see LICENSE file for more details.
+
+# Translate JavaScript strings
+# 1) Navigate to the directory:
+#    cd src/lib/translations/messages
+# 2) Install i18n dev dependencies
+#    npm install
+# 3) Add a new language
+#    npm run init_catalog lang <lang>
+# 4) Extract translation keys/values
+#    $ npm run extract_messages
+# 5) Install the transifex-client
+#    see: https://developers.transifex.com/docs/cli#transifex-client
+# 6) Push source (.pot) and translations (.po) to Transifex
+#    Navigate to the root of the invenio_administration repository
+#    $ tx push -s -t
+# 7) Pull translations for a single language from Transifex
+#    $ tx pull -l <lang>
+# 8) Pull translations for all languages from Transifex
+#    $ tx pull -a
+# 9) Compile .po files for all languages
+#    $ npm run compile_catalog
+# 10) Convert .po file for a single language
+#    $ npm run compile_catalog lang <lang>
+
+[main]
+host = https://app.transifex.com
+
+[o:inveniosoftware:p:invenio:r:react-searchkit-messages-ui]
+file_filter = src/lib/translations/messages/<lang>/messages.po
+source_file = src/lib/translations/translations.pot
+source_lang = en
+type = PO

i18next-scanner.config.js

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+// This file is part of React-Searchkit
+// Copyright (C) 2021 Graz University of Technology.
+//
+// React-Searchkit is free software; you can redistribute it and/or modify it
+// under the terms of the MIT License; see LICENSE file for more details.
+
+const { languages } = require("./package").config;
+
+// list of func used to
+// mark the strings for translation
+const funcList = ["i18next.t"];
+
+// list of extension to look for
+const extensions = [".js", ".jsx"];
+
+module.exports = {
+  options: {
+    debug: true,
+    removeUnusedKeys: true,
+    browserLanguageDetection: true,
+    func: {
+      list: funcList,
+      extensions: extensions,
+    },
+    //using Trans component
+    trans: {
+      component: "Trans",
+      extensions: extensions,
+      fallbackKey: function (ns, value) {
+        return value;
+      },
+    },
+    lngs: languages,
+    ns: [
+      // file name (.json)
+      "translations",
+    ],
+    defaultLng: "en",
+    defaultNs: "translations",
+    // @param {string} lng The language currently used.
+    // @param {string} ns The namespace currently used.
+    // @param {string} key The translation key.
+    // @return {string} Returns a default value for the translation key.
+    defaultValue: function (lng, ns, key) {
+      if (lng === "en") {
+        // Return key as the default value for English language
+        return key;
+      }
+      return "";
+    },
+    resource: {
+      // The path where resources get loaded from. Relative to current working directory.
+      loadPath: "src/lib/translations/messages/{{lng}}/{{ns}}.json",
+
+      // The path to store resources.
+      savePath: "src/lib/translations/messages/{{lng}}/{{ns}}.json",
+
+      jsonIndent: 2,
+      lineEnding: "\n",
+    },
+    nsSeparator: false, // namespace separator
+
+    //Set to false to disable key separator
+    // if you prefer having keys as the fallback for translation (e.g. gettext).
+    keySeparator: false,
+  },
+};