fix: update iOS platform version and enable sentence capitalization in chat input fields

ios/Podfile

@@ -1,4 +1,4 @@
-platform :ios, '12.0'
+platform :ios, '15.5'
 
 ENV['COCOAPODS_DISABLE_STATS'] = 'true'
 

lib/screens/channel_chat_screen.dart

@@ -727,6 +727,7 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
                   inputFormatters: [
                     Utf8LengthLimitingTextInputFormatter(maxBytes),
                   ],
+                  textCapitalization: TextCapitalization.sentences,
                   decoration: InputDecoration(
                     hintText: context.l10n.chat_typeMessage,
                     border: OutlineInputBorder(

lib/screens/chat_screen.dart

@@ -281,6 +281,7 @@ class _ChatScreenState extends State<ChatScreen> {
                     inputFormatters: [
                       Utf8LengthLimitingTextInputFormatter(maxBytes),
                     ],
+                    textCapitalization: TextCapitalization.sentences,
                     decoration: InputDecoration(
                       hintText: context.l10n.chat_typeMessage,
                       border: const OutlineInputBorder(),