refactor: change the "copy" text to "copy URL" for added context

app/src/main/res/layout/fragment_modal_url_bottom_sheet.xml

@@ -7,8 +7,7 @@
     app:behavior_hideable="true"
     app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior"
     android:gravity="center_horizontal"
-    android:paddingVertical="@dimen/large_spacing"
-    >
+    android:paddingVertical="@dimen/large_spacing">
 
     <TextView
         android:id="@+id/openURLTitleTextView"
@@ -43,7 +42,7 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         style="@style/BottomSheetActionItem"
-        android:text="@string/copy"
+        android:text="@string/copy_url"
         />
 
     <TextView

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

@@ -872,6 +872,7 @@
     <string name="dialog_open_url_title">Open URL?</string>
     <string name="dialog_open_url_explanation">Are you sure you want to open %s?</string>
     <string name="open">Open</string>
+    <string name="copy_url">Copy URL</string>
 
     <string name="dialog_link_preview_title">Enable Link Previews?</string>
     <string name="dialog_link_preview_explanation">Enabling link previews will show previews for URLs you send and receive. This can be useful, but Session will need to contact linked websites to generate previews. You can always disable link previews in Session\'s settings.</string>