action_sheet: Add 'Channel feed' button to channel action sheet#1794

chrisbobbe wants to merge 4 commits intozulip:mainzulip/zulip-flutter:mainfrom

chrisbobbe:pr-channel-feed-button-in-action-sheetchrisbobbe/zulip-flutter:pr-channel-feed-button-in-action-sheetCopy head branch name to clipboard