Remove several unused resources

Unused resources make applications larger and slow down builds.
This commit removes several unused resources marked
by the linter in Android Studio (UnusedResources warn).

Related to https://github.com/kiwix/kiwix-android/issues/98

app/src/main/res/values/colors.xml

@@ -9,7 +9,6 @@
   <color name="primary_text">#212121</color>
   <color name="secondary_text">#727272</color>
   <color name="icons">#212121</color>
-  <color name="divider">#304e9a</color>
   <color name="white">#fafafa</color>
   <color name="gray_list_bg">#0d000000</color>
   <color name="drawer_background_day">#ffffff</color>
@@ -22,9 +21,6 @@
   <color name="blue_grey">#ECEFF1</color>
   <color name="foreground_material_dark">@android:color/white</color>
   <color name="back_to_top_background">#DDFFFFFF</color>
-  <color name="back_to_top_text">@android:color/black</color>
-  <color name="back_to_top_background_night">#FF000000</color>
-  <color name="back_to_top_text_night">#FFFFFFFF</color>
   <color name="picture_label">#fb8c00</color>
   <color name="video_label">#651FFF</color>
   <color name="blue800">#1565c0</color>

app/src/main/res/values/dimens.xml

@@ -5,11 +5,6 @@
   <dimen name="activity_vertical_margin">16dp</dimen>
   <dimen name="dimen_small_padding">4dp</dimen>
   <dimen name="dimen_medium_padding">8dp</dimen>
-  <dimen name="dimen_1dp">1dp</dimen>
-  <dimen name="dimen_0dp">0dp</dimen>
-  <dimen name="language_name_localized_text_size">14sp</dimen>
-  <dimen name="language_name_margin_left">10dp</dimen>
-  <dimen name="navigation_width">260dp</dimen>
   <dimen name="abc_dropdownitem_text_padding_left">8dip</dimen>
   <dimen name="abc_dropdownitem_text_padding_right">8dip</dimen>
   <dimen name="library_textview_padding">75dp</dimen>
@@ -17,9 +12,7 @@
   <dimen name="library_article_list_padding">60dp</dimen>
   <dimen name="network_permission_text_margin_top">200dp</dimen>
   <dimen name="network_permission_button_margin_top">230dp</dimen>
-  <dimen name="bookmark_title_text_size">15sp</dimen>
   <dimen name="download_management_no_downloads_padding_bottom">75dp</dimen>
-  <dimen name="help_cardview_card_elevation">2dp</dimen>
   <dimen name="kiwix_search_widget_layout_id_height">50dp</dimen>
   <dimen name="file_management_no_files_padding_bottom">75dp</dimen>
   <dimen name="file_management_no_files_text_size">20sp</dimen>
@@ -29,48 +22,25 @@
   <dimen name="fullscreen_control_button_margin">7dp</dimen>
   <dimen name="download_progress_padding">1dp</dimen>
   <dimen name="kiwix_search_widget_margin">1dp</dimen>
-  <dimen name="get_content_card_margin">3dp</dimen>
   <dimen name="progress_view_height">3dp</dimen>
-  <dimen name="language_entries_count_margin_right">16dp</dimen>
   <dimen name="title_text_margin">16dp</dimen>
   <dimen name="title_text_padding">16dp</dimen>
   <dimen name="slider_dialog_horizontal_padding">16dp</dimen>
-  <dimen name="get_content_card_text_size">20sp</dimen>
   <dimen name="download_management_no_downloads_text_size">20sp</dimen>
-  <dimen name="language_check_item_text_size">18sp</dimen>
-  <dimen name="left_drawer_list_height">0dp</dimen>
   <dimen name="download_item_layout_width">0dp</dimen>
   <dimen name="kiwix_search_widget_padding">0dp</dimen>
-  <dimen name="activity_bookmarks_img_width">100dp</dimen>
-  <dimen name="activity_bookmarks_img_height">100dp</dimen>
-  <dimen name="bookmark_tab_icon_width">24dp</dimen>
-  <dimen name="bookmark_tab_icon_height">24dp</dimen>
-  <dimen name="language_entries_count_vertical_margin">6dp</dimen>
   <dimen name="section_list_height">56dp</dimen>
-  <dimen name="tabs_list_height">56dp</dimen>
   <dimen name="favicon_width">48dp</dimen>
-  <dimen name="exit_button_width">48dp</dimen>
-  <dimen name="exit_button_height">48dp</dimen>
-  <dimen name="help_cardview_horizontal_padding">20dp</dimen>
   <dimen name="progressbar_padding">20dp</dimen>
   <dimen name="pause_min_height">35dp</dimen>
   <dimen name="pause_min_width">35dp</dimen>
   <dimen name="stop_min_height">35dp</dimen>
   <dimen name="stop_min_width">35dp</dimen>
   <dimen name="slider_preference_seekbar_horizontal_padding">12dp</dimen>
-  <dimen name="exit_button_padding">12dp</dimen>
-  <dimen name="activity_bookmarks_vertical_padding">15dp</dimen>
-  <dimen name="bookmark_title_margin">15dp</dimen>
-  <dimen name="language_checkbox_margin_left">15dp</dimen>
   <dimen name="zim_list_vertical_padding">15dp</dimen>
-  <dimen name="help_cardview_card_corner_radius">4dp</dimen>
-  <dimen name="exit_button_margin_right">4dp</dimen>
   <dimen name="favicon_margin_right">8dp</dimen>
   <dimen name="stop_horizontal_margin">8dp</dimen>
-  <dimen name="activity_bookmarks_horizontal_padding">10dp</dimen>
   <dimen name="zim_list_horizontal_padding">10dp</dimen>
-  <dimen name="language_name_localized_margin_left">10dp</dimen>
-  <dimen name="help_textview_padding">10dp</dimen>
   <dimen name="progressbar_textview_vertical_padding">10dp</dimen>
   <dimen name="bottom_toolbar_height">48dp</dimen>
   <!-- Workaround to store floats in dimen -->

app/src/main/res/values/ic_kiwix_background.xml

@@ -1,4 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<resources>
-    <color name="ic_kiwix_background">#FFFFFF</color>
-</resources>