[doc] Update translations doc to explain how to enable new language on Android

Signed-off-by: Jean-Baptiste <jeanbaptiste.charron@outlook.fr>

android/app/src/main/java/app/organicmaps/bookmarks/ChooseBookmarkCategoryFragment.java

@@ -42,7 +42,7 @@ public class ChooseBookmarkCategoryFragment
   public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
   {
     View root = inflater.inflate(R.layout.choose_bookmark_category_fragment, container, false);
-    getDialog().getWindow().setBackgroundDrawableResource(R.drawable.bg_transparent_dlg);
+    getDialog().getWindow().setBackgroundDrawableResource(android.R.color.transparent);
     mRecycler = root.findViewById(R.id.recycler);
     mRecycler.setLayoutManager(new LinearLayoutManager(requireActivity()));
     return root;

android/app/src/main/java/app/organicmaps/bookmarks/ChooseBookmarksSortingTypeFragment.java

@@ -77,7 +77,7 @@ public class ChooseBookmarksSortingTypeFragment
   public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState)
   {
     super.onViewCreated(view, savedInstanceState);
-    getDialog().getWindow().setBackgroundDrawableResource(R.drawable.bg_transparent_dlg);
+    getDialog().getWindow().setBackgroundDrawableResource(android.R.color.transparent);
 
     final Bundle args = getArguments();
     if (args == null)

android/app/src/main/java/app/organicmaps/widget/StackedButtonsDialog.java

@@ -61,7 +61,7 @@ public class StackedButtonsDialog extends AppCompatDialog implements View.OnClic
     setCancelable(mCancelable);
     setOnCancelListener(mCancelListener);
     setContentView(R.layout.dialog_stacked_buttons);
-    getWindow().setBackgroundDrawableResource(R.drawable.bg_transparent_dlg);
+    getWindow().setBackgroundDrawableResource(android.R.color.transparent);
 
     TextView title = findViewById(R.id.tv__title);
     UiUtils.setTextAndHideIfEmpty(title, mTitle);

android/app/src/main/res/drawable/bg_transparent_dlg.xml

@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<shape xmlns:android="http://schemas.android.com/apk/res/android">
-    <solid android:color="@android:color/transparent"/>
-    <corners android:radius="28dp"/>
-</shape>

docs/TRANSLATIONS.md

@@ -130,6 +130,11 @@ The recommended approach for resolving conflicts is as follows:
 
 Using these steps all existing translations can still be kept and rebased into the repo, without losing work. The important bit is that you need to ensure that all translations are in the Weblate-internal git repository before you rebase, so that they get into the _actual_ Codeberg repo. 
 
+### Add support of new language in Android app
+1. Make sure Weblate has generate strings.xml for your language in this directory [android/app/src/main/res/values\*/strings.xml][android_git]
+2. Add the language in `localeFilters` list in [build.gradle](https://codeberg.org/comaps/comaps/src/commit/e156d21eee7debd13ce9ec775cdcb264a97aad47/android/app/build.gradle#L258) (It's necessary to add language in this file to be sure app translations and library translations was integrated in the app).
+3. Add the language in [locales_config.xml](https://codeberg.org/comaps/comaps/src/branch/main/android/app/src/main/res/xml/locales_config.xml) (It's necessary to allow users to change app language in Android settings on most recent devices).
+
 [codeberg_translate]: https://translate.codeberg.org/projects/comaps/
 [contribute]: https://docs.weblate.org/en/latest/workflows.html
 [android_weblate]: https://translate.codeberg.org/projects/comaps/android/