This commit changes the composer to not be read-only on the server
buffer, which tells the user that they can send commands from that view.
On the server buffer, the placeholder is changed to
"Type a command (see /help)", which indicates to the user that this buffer
only accepts commands, and gives them a hint for how to learn what
commands are available.
Implements: https://todo.sr.ht/~emersion/gamja/38
Instead of focusing the composer, focus the buffer scrollview when
switching to a buffer. This allows keyboard navigation to work as
expected, with arrow up/down and page up/down scrolling the buffer
instead of doing nothing.
Focus back the composer when a KeyboardEvent produces text. This
allows users to start typing a message right after switching to a
buffer.
Closes: https://todo.sr.ht/~emersion/gamja/64
