App polish part 2 (#1118)

- Fix sheet backgrounds in dark mode.
- Fix background colours for reaction buttons.
- Reply view layout.
- Update separator colours.
- Don't show sender name/avatar in DMs.
- Fix inconsistent line heights with formatted body text.
- Use plain text for reply
- Increase tappable size of collapsed state changes button.
- Blockquote layout and text colour.
- Tap to expand the topic in room details.
- Change the topic and security font size in room details.
- Add cancel button when inviting someone to an existing room.
- Reword Add Friends to Add People in start chat screen.
- Update compound.

ElementX/Sources/Screens/StartChatScreen/View/StartChatScreen.swift

@@ -79,7 +79,7 @@ struct StartChatScreen: View {
     private var inviteFriendsSection: some View {
         Section {
             MatrixUserShareLink(userID: context.viewState.userID) {
-                Label(L10n.actionInviteFriendsToApp(InfoPlistReader.main.bundleDisplayName), systemImage: "square.and.arrow.up")
+                Label(L10n.actionInvitePeopleToApp(InfoPlistReader.main.bundleDisplayName), systemImage: "square.and.arrow.up")
             }
             .buttonStyle(FormButtonStyle())
             .accessibilityIdentifier(A11yIdentifiers.startChatScreen.inviteFriends)