[NEW] Allows agents to send chat transcript to omnichannel end-users (#17774)

app/authorization/server/startup.js

app/livechat/client/views/app/tabbar/visitorInfo.html

app/livechat/client/views/app/tabbar/visitorInfo.js

app/livechat/client/views/app/tabbar/visitorTranscript.html

app/livechat/client/views/app/tabbar/visitorTranscript.js

app/livechat/client/views/regular.js

app/livechat/lib/messageTypes.js

app/livechat/server/hooks/sendTranscriptOnClose.js

app/livechat/server/index.js

app/livechat/server/lib/Livechat.js

app/livechat/server/methods/discardTranscript.js

app/livechat/server/methods/requestTranscript.js

app/livechat/server/methods/sendTranscript.js

app/models/server/models/LivechatRooms.js

app/models/server/models/Messages.js

packages/rocketchat-i18n/i18n/en.i18n.json

packages/rocketchat-i18n/i18n/pt-BR.i18n.json

server/publications/room/index.js