i18n: translate the chat composer and messages

Catching up on the fork's rule that every update also translates one existing
system — three updates went by without one.

The composer's placeholder takes the channel as a parameter rather than being
concatenated, since Portuguese puts the channel elsewhere in the sentence than
English does.

The translation hook is bound to `tr` in these two files, not `t`: both already
use `t` for transfer records in inner scopes, which shadowed the function and
made it uncallable exactly where it was needed.

packages/web/src/i18n/locales/en.ts

@@ -56,6 +56,25 @@ export const en = {
   'accountMenu.copyId': 'Copy User ID',
   'accountMenu.copied': 'Copied',
 
+  // Chat — composer and messages
+  'chat.composer.placeholder': 'Message {channel}',
+  'chat.composer.attach': 'Attach file',
+  'chat.composer.emoji': 'Emoji',
+  'chat.composer.gif': 'GIF',
+  'chat.composer.gifPicker': 'GIF picker',
+  'chat.composer.emojiPicker': 'Emoji picker',
+  'chat.composer.send': 'Send',
+  'chat.composer.sendMessage': 'Send message',
+  'chat.composer.uploading': 'Uploading',
+  'chat.composer.uploadingEllipsis': 'Uploading…',
+  'chat.composer.removeAttachment': 'Remove attachment',
+  'chat.composer.failedAttachment': 'Remove or retry the failed attachment to send',
+  'chat.composer.replyingTo': 'Replying to',
+  'chat.composer.cancelReply': 'Cancel reply',
+  'chat.message.addReaction': 'Add reaction',
+  'chat.message.edit': 'Edit',
+  'chat.message.reply': 'Reply',
+
   // Statistics
   'stats.title': 'Statistics',
   'stats.range.7': 'Last 7 days',